 <p>this is the class :</p> <pre><code>&lt;?php class WebDirect_CustomPrice_Model_Sales_Quote_Item extends Mage_Sales_Model_Quote_Item { public function representProduct($product) { $parentResult = parent::representProduct($product); //if parent result is already false, we already have a different product, exit. if ($parentResult === false) { return $parentResult; } $itemProduct = $this-&gt;getProduct(); /* * do our check for 'same product' here. * Returns true if attribute is the same thus it is hte same product */ if ($product-&gt;getPrice() == $itemProduct-&gt;getPrice()) { return true; //same product } else { return false; //different product } } } </code></pre>