diff --git a/spec/Condition/NotInSpec.php b/spec/Condition/NotInSpec.php
index 0bca1e1..d18105d 100644
--- a/spec/Condition/NotInSpec.php
+++ b/spec/Condition/NotInSpec.php
@@ -6,7 +6,6 @@
 use Doctrine\ORM\Query\Expr;
 use Doctrine\ORM\QueryBuilder;
 use PhpSpec\ObjectBehavior;
-use Rb\Specification\Doctrine\Condition\In;
 use Rb\Specification\Doctrine\SpecificationInterface;
 
 class NotInSpec extends ObjectBehavior
@@ -23,7 +22,6 @@ public function let()
     public function it_is_an_expression()
     {
         $this->shouldBeAnInstanceOf(SpecificationInterface::class);
-        $this->shouldBeAnInstanceOf(In::class);
     }
 
     public function it_returns_an_expression_func_object(QueryBuilder $queryBuilder, ArrayCollection $parameters, Expr $expr)
diff --git a/src/Condition/Between.php b/src/Condition/Between.php
index eca0c45..846f975 100644
--- a/src/Condition/Between.php
+++ b/src/Condition/Between.php
@@ -4,9 +4,12 @@
 
 use Doctrine\ORM\QueryBuilder;
 use Rb\Specification\Doctrine\AbstractSpecification;
+use Rb\Specification\Doctrine\Helper\ParameterTrait;
 
 class Between extends AbstractSpecification
 {
+    use ParameterTrait;
+
     /**
      * @var mixed
      */
@@ -36,8 +39,8 @@ public function __construct($field, $from, $to, $dqlAlias = null)
      */
     public function modify(QueryBuilder $queryBuilder, $dqlAlias)
     {
-        $fromParam = $this->generateParameterName('from', $queryBuilder);
-        $toParam   = $this->generateParameterName('to', $queryBuilder);
+        $fromParam = $this->generateParameterName($queryBuilder, 'from');
+        $toParam   = $this->generateParameterName($queryBuilder, 'to');
 
         $queryBuilder->setParameter($fromParam, $this->from);
         $queryBuilder->setParameter($toParam, $this->to);
@@ -48,15 +51,4 @@ public function modify(QueryBuilder $queryBuilder, $dqlAlias)
             sprintf(':%s', $toParam)
         );
     }
-
-    /**
-     * @param string       $type
-     * @param QueryBuilder $queryBuilder
-     *
-     * @return string
-     */
-    private function generateParameterName($type, QueryBuilder $queryBuilder)
-    {
-        return sprintf('%s_%d', $type, count($queryBuilder->getParameters()));
-    }
 }
diff --git a/src/Condition/Comparison.php b/src/Condition/Comparison.php
index 4b0b525..91f2005 100644
--- a/src/Condition/Comparison.php
+++ b/src/Condition/Comparison.php
@@ -6,9 +6,14 @@
 use Doctrine\ORM\QueryBuilder;
 use Rb\Specification\Doctrine\AbstractSpecification;
 use Rb\Specification\Doctrine\Exception\InvalidArgumentException;
+use Rb\Specification\Doctrine\Helper\ParameterTrait;
+use Rb\Specification\Doctrine\Helper\ValueTrait;
 
 class Comparison extends AbstractSpecification
 {
+    use ParameterTrait;
+    use ValueTrait;
+
     const EQ   = '=';
     const NEQ  = '<>';
     const LT   = '<';
@@ -22,11 +27,6 @@ class Comparison extends AbstractSpecification
      */
     protected static $operators = [self::EQ, self::NEQ, self::LT, self::LTE, self::GT, self::GTE, self::LIKE];
 
-    /**
-     * @var string
-     */
-    protected $value;
-
     /**
      * @var string
      */
@@ -53,7 +53,7 @@ public function __construct($operator, $field, $value, $dqlAlias = null)
         }
 
         $this->operator = $operator;
-        $this->value    = $value;
+        $this->setValue($value);
 
         parent::__construct($field, $dqlAlias);
     }
@@ -68,8 +68,8 @@ public function __construct($operator, $field, $value, $dqlAlias = null)
      */
     public function modify(QueryBuilder $queryBuilder, $dqlAlias)
     {
-        $paramName = $this->generateParameterName($queryBuilder);
-        $queryBuilder->setParameter($paramName, $this->value);
+        $paramName = $this->generateParameterName($queryBuilder, 'comparison');
+        $queryBuilder->setParameter($paramName, $this->getValue());
 
         return (string) new DoctrineComparison(
             $this->createPropertyWithAlias($dqlAlias),
@@ -77,16 +77,4 @@ public function modify(QueryBuilder $queryBuilder, $dqlAlias)
             sprintf(':%s', $paramName)
         );
     }
-
-    /**
-     * Return automatically generated parameter name.
-     *
-     * @param QueryBuilder $queryBuilder
-     *
-     * @return string
-     */
-    protected function generateParameterName(QueryBuilder $queryBuilder)
-    {
-        return sprintf('comparison_%d', count($queryBuilder->getParameters()));
-    }
 }
diff --git a/src/Condition/EqualsProperty.php b/src/Condition/EqualsProperty.php
index 138f9f6..659d9cf 100644
--- a/src/Condition/EqualsProperty.php
+++ b/src/Condition/EqualsProperty.php
@@ -28,7 +28,7 @@ public function modify(QueryBuilder $queryBuilder, $dqlAlias)
         return (string) new DoctrineComparison(
             $this->createPropertyWithAlias($dqlAlias),
             $this->operator,
-            $this->createAliasedName($this->value, $dqlAlias)
+            $this->createAliasedName($this->getValue(), $dqlAlias)
         );
     }
 }
diff --git a/src/Condition/In.php b/src/Condition/In.php
index ec77449..c0048e0 100644
--- a/src/Condition/In.php
+++ b/src/Condition/In.php
@@ -4,13 +4,13 @@
 
 use Doctrine\ORM\QueryBuilder;
 use Rb\Specification\Doctrine\AbstractSpecification;
+use Rb\Specification\Doctrine\Helper\ParameterTrait;
+use Rb\Specification\Doctrine\Helper\ValueTrait;
 
 class In extends AbstractSpecification
 {
-    /**
-     * @var mixed
-     */
-    protected $value;
+    use ParameterTrait;
+    use ValueTrait;
 
     /**
      * @param string      $field
@@ -19,7 +19,7 @@ class In extends AbstractSpecification
      */
     public function __construct($field, $value, $dqlAlias = null)
     {
-        $this->value = $value;
+        $this->setValue($value);
 
         parent::__construct($field, $dqlAlias);
     }
@@ -29,22 +29,12 @@ public function __construct($field, $value, $dqlAlias = null)
      */
     public function modify(QueryBuilder $queryBuilder, $dqlAlias)
     {
-        $paramName = $this->generateParameterName($queryBuilder);
-        $queryBuilder->setParameter($paramName, $this->value);
+        $paramName = $this->generateParameterName($queryBuilder, 'in');
+        $queryBuilder->setParameter($paramName, $this->getValue());
 
         return (string) $queryBuilder->expr()->in(
             $this->createPropertyWithAlias($dqlAlias),
             sprintf(':%s', $paramName)
         );
     }
-
-    /**
-     * @param QueryBuilder $queryBuilder
-     *
-     * @return string
-     */
-    protected function generateParameterName(QueryBuilder $queryBuilder)
-    {
-        return sprintf('in_%d', count($queryBuilder->getParameters()));
-    }
 }
diff --git a/src/Condition/IsInstanceOf.php b/src/Condition/IsInstanceOf.php
index 04f377d..5e65417 100644
--- a/src/Condition/IsInstanceOf.php
+++ b/src/Condition/IsInstanceOf.php
@@ -4,13 +4,11 @@
 
 use Doctrine\ORM\QueryBuilder;
 use Rb\Specification\Doctrine\AbstractSpecification;
+use Rb\Specification\Doctrine\Helper\ValueTrait;
 
 class IsInstanceOf extends AbstractSpecification
 {
-    /**
-     * @var string
-     */
-    private $className;
+    use ValueTrait;
 
     /**
      * @param string $field
@@ -19,7 +17,7 @@ class IsInstanceOf extends AbstractSpecification
      */
     public function __construct($field, $className, $dqlAlias = null)
     {
-        $this->className = $className;
+        $this->setValue($className);
 
         parent::__construct($field, $dqlAlias);
     }
@@ -31,7 +29,7 @@ public function modify(QueryBuilder $queryBuilder, $dqlAlias)
     {
         return (string) $queryBuilder->expr()->isInstanceOf(
             $this->createPropertyWithAlias($dqlAlias),
-            $this->className
+            $this->getValue()
         );
     }
 }
diff --git a/src/Condition/IsNotNull.php b/src/Condition/IsNotNull.php
index 0d446d8..8e4b13c 100644
--- a/src/Condition/IsNotNull.php
+++ b/src/Condition/IsNotNull.php
@@ -3,8 +3,9 @@
 namespace Rb\Specification\Doctrine\Condition;
 
 use Doctrine\ORM\QueryBuilder;
+use Rb\Specification\Doctrine\AbstractSpecification;
 
-class IsNotNull extends IsNull
+class IsNotNull extends AbstractSpecification
 {
     /**
      * {@inheritdoc}
diff --git a/src/Condition/NotIn.php b/src/Condition/NotIn.php
index 77a5b47..7fbfe69 100644
--- a/src/Condition/NotIn.php
+++ b/src/Condition/NotIn.php
@@ -3,27 +3,35 @@
 namespace Rb\Specification\Doctrine\Condition;
 
 use Doctrine\ORM\QueryBuilder;
+use Rb\Specification\Doctrine\AbstractSpecification;
+use Rb\Specification\Doctrine\Helper\ParameterTrait;
+use Rb\Specification\Doctrine\Helper\ValueTrait;
 
-class NotIn extends In
+class NotIn extends AbstractSpecification
 {
+    use ValueTrait;
+    use ParameterTrait;
+
+    /**
+     * @param string      $field
+     * @param mixed       $value
+     * @param string|null $dqlAlias
+     */
+    public function __construct($field, $value, $dqlAlias = null)
+    {
+        $this->setValue($value);
+
+        parent::__construct($field, $dqlAlias);
+    }
+
     public function modify(QueryBuilder $queryBuilder, $dqlAlias)
     {
-        $paramName = $this->generateParameterName($queryBuilder);
-        $queryBuilder->setParameter($paramName, $this->value);
+        $paramName = $this->generateParameterName($queryBuilder, 'not_in');
+        $queryBuilder->setParameter($paramName, $this->getValue());
 
         return (string) $queryBuilder->expr()->notIn(
             $this->createPropertyWithAlias($dqlAlias),
             sprintf(':%s', $paramName)
         );
     }
-
-    /**
-     * @param QueryBuilder $queryBuilder
-     *
-     * @return string
-     */
-    protected function generateParameterName(QueryBuilder $queryBuilder)
-    {
-        return sprintf('not_in_%d', count($queryBuilder->getParameters()));
-    }
 }
diff --git a/src/Helper/ParameterTrait.php b/src/Helper/ParameterTrait.php
new file mode 100644
index 0000000..292d4e3
--- /dev/null
+++ b/src/Helper/ParameterTrait.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace Rb\Specification\Doctrine\Helper;
+
+use Doctrine\ORM\QueryBuilder;
+
+trait ParameterTrait
+{
+    /**
+     * Return automatically generated parameter name.
+     *
+     * @param QueryBuilder $queryBuilder
+     * @param string|null  $name
+     *
+     * @return string
+     */
+    protected function generateParameterName(QueryBuilder $queryBuilder, $name = null)
+    {
+        if (null === $name) {
+            $name = get_class($this);
+        }
+
+        return sprintf('%s_%d', $name, count($queryBuilder->getParameters()));
+    }
+}
diff --git a/src/Helper/TypeCheckerTrait.php b/src/Helper/TypeCheckerTrait.php
new file mode 100644
index 0000000..8d75db6
--- /dev/null
+++ b/src/Helper/TypeCheckerTrait.php
@@ -0,0 +1,36 @@
+<?php
+
+namespace Rb\Specification\Doctrine\Helper;
+
+use Rb\Specification\Doctrine\Exception\InvalidArgumentException;
+
+trait TypeCheckerTrait
+{
+    /**
+     * @var string[]
+     */
+    protected $validTypes;
+
+    /**
+     * @var string
+     */
+    private $type;
+
+    /**
+     * @param string $type
+     *
+     * @throws InvalidArgumentException
+     */
+    public function setType($type)
+    {
+        if (! in_array($type, $this->validTypes, true)) {
+            throw new InvalidArgumentException(sprintf(
+                '"%s" is not a valid type! Valid types: %s',
+                $type,
+                implode(', ', $this->validTypes)
+            ));
+        }
+
+        $this->type = $type;
+    }
+}
diff --git a/src/Helper/ValueTrait.php b/src/Helper/ValueTrait.php
new file mode 100644
index 0000000..8a2e0fe
--- /dev/null
+++ b/src/Helper/ValueTrait.php
@@ -0,0 +1,27 @@
+<?php
+
+namespace Rb\Specification\Doctrine\Helper;
+
+trait ValueTrait
+{
+    /**
+     * @var mixed
+     */
+    private $value;
+
+    /**
+     * @return string
+     */
+    protected function getValue()
+    {
+        return $this->value;
+    }
+
+    /**
+     * @param mixed $value
+     */
+    protected function setValue($value)
+    {
+        $this->value = $value;
+    }
+}
diff --git a/src/Query/GroupBy.php b/src/Query/GroupBy.php
index 9b1515b..fee5b8e 100644
--- a/src/Query/GroupBy.php
+++ b/src/Query/GroupBy.php
@@ -4,21 +4,20 @@
 
 use Doctrine\ORM\QueryBuilder;
 use Rb\Specification\Doctrine\AbstractSpecification;
-use Rb\Specification\Doctrine\Exception\InvalidArgumentException;
+use Rb\Specification\Doctrine\Helper\TypeCheckerTrait;
 
 /**
  * @author  Kyle Tucker <kyleatucker@gmail.com>
  */
 class GroupBy extends AbstractSpecification
 {
+    use TypeCheckerTrait;
+
     const GROUP_BY     = 'groupBy';
     const ADD_GROUP_BY = 'addGroupBy';
 
     /** @var string[] */
-    protected static $types = [self::GROUP_BY, self::ADD_GROUP_BY];
-
-    /** @var string */
-    protected $type;
+    protected $validTypes = [self::GROUP_BY, self::ADD_GROUP_BY];
 
     /**
      * Constructor.
@@ -45,22 +44,4 @@ public function modify(QueryBuilder $queryBuilder, $dqlAlias)
             ]
         );
     }
-
-    /**
-     * @param string $type
-     *
-     * @throws InvalidArgumentException
-     */
-    public function setType($type)
-    {
-        if (! in_array($type, self::$types, true)) {
-            throw new InvalidArgumentException(sprintf(
-                '"%s" is not a valid type! Valid types: %s',
-                $type,
-                implode(', ', self::$types)
-            ));
-        }
-
-        $this->type = $type;
-    }
 }
diff --git a/src/Query/Select.php b/src/Query/Select.php
index 449c74c..196ef9c 100644
--- a/src/Query/Select.php
+++ b/src/Query/Select.php
@@ -3,7 +3,7 @@
 namespace Rb\Specification\Doctrine\Query;
 
 use Doctrine\ORM\QueryBuilder;
-use Rb\Specification\Doctrine\Exception\InvalidArgumentException;
+use Rb\Specification\Doctrine\Helper\TypeCheckerTrait;
 use Rb\Specification\Doctrine\SpecificationInterface;
 
 /**
@@ -11,21 +11,18 @@
  */
 class Select implements SpecificationInterface
 {
+    use TypeCheckerTrait;
+
     const SELECT     = 'select';
     const ADD_SELECT = 'addSelect';
 
-    protected static $types = [self::SELECT, self::ADD_SELECT];
+    protected $validTypes = [self::SELECT, self::ADD_SELECT];
 
     /**
      * @var string|array
      */
     protected $select;
 
-    /**
-     * @var string
-     */
-    protected $type;
-
     /**
      * @param string|array $select
      * @param string       $type
@@ -44,24 +41,6 @@ public function modify(QueryBuilder $queryBuilder, $dqlAlias)
         call_user_func_array([$queryBuilder, $this->type], [$this->select]);
     }
 
-    /**
-     * @param string $type
-     *
-     * @throws InvalidArgumentException
-     */
-    public function setType($type)
-    {
-        if (! in_array($type, self::$types, true)) {
-            throw new InvalidArgumentException(sprintf(
-                '"%s" is not a valid type! Valid types: %s',
-                $type,
-                implode(', ', self::$types)
-            ));
-        }
-
-        $this->type = $type;
-    }
-
     /**
      * {@inheritdoc}
      */