<?php
    $thumb_image = wp_get_attachment_image_src( $attachment->ID, apply_filters( 'single_product_small_thumbnail_size', 'shop_thumbnail' ), false );
    theme_product_image_@(id)( wp_get_attachment_url( $attachment->ID ),
                                    esc_attr( $attachment->post_title ),
                                    implode(' ', $classes),
                                    $thumb_image);
?>