Event.observe(document,'dom:loaded',function (event) {
    $$('.viberite input').each(function (element) {
        Event.observe(element,'click',function (event) {
            el = event.element();
            if (el.checked) {
                path = $$('#product img')[0].src.split('/')
                size = path[path.length-3];
                $$('#product img')[0].src = '/thumbs/'+size+'/'+el.value+'/';
            }
        });
    });
});