$image       = wp_get_attachment_image( $attachment_id, apply_filters( 'single_product_small_thumbnail_size', 'shop_thumbnail' ) );
            $image_class = esc_attr( implode( ' ', $classes ) );
            $image_title = esc_attr( get_the_title( $attachment_id ) );

            echo apply_filters( 'woocommerce_single_product_image_thumbnail_html', sprintf( '<a href="%s" class="%s" title="%s"  rel="prettyPhoto[product-gallery]">%s</a>', $image_link, $image_class, $image_title, $image ), $attachment_id, $post->ID, $image_class );