<form class="form-horizontal ms2_form msoptionsprice-product" method="post">
    <input type="hidden" name="id" value="{$_modx->resource.id}"/>
    <input type="hidden" name="mssetincart_set" value="{$_modx->resource.id}"/>
    <input type="hidden" name="count" value="1"/>
    <div class="multiple-checkout">
        <div class="buttons-set title-buttons">
            <button class="button btn-continue" title="{'ms2_cart_button_all' | lexicon}" name="ms2_action" value="cart/add" type="submit">
                <span>{'ms2_cart_button_all' | lexicon}</span>
            </button>
        </div>
    </div>
</form>

{'!msSetInCart.set' | snippet : [
    'link' => 3,
    'setActive' => 1,
    'setMode' => 'cart',
    'setInput' => 'checkbox',
    'sortdir' => 'DESC',
    'tpl' => 'tpl.msSetInCart.set'
]}