Some themes add custom classes to their catalog ‘add to cart’ buttons. If you’ve installed WooCommerce Show Single Variations, you may notice those buttons don’t have those classes applied. Fortunately, it’s easy to add them.

Using a tool like Code Snippets, add the following function:

/*
 * Add custom button class
 *
 * @param string $class
 *
 * @return string
 */
function iconic_button_class( $class ) {	
	$class .= ' your-custom-class';
	return $class;
}

add_filter( 'jck_wssv_add_to_cart_button_class', 'iconic_button_class', 10 );

This will append your-custom-class to the button classes. Note that there is space at the beginning of this custom class.