- We're sorry, but this product is an 'add-on' - include any of the following items to your basket first to purchase this:<br><br> Petzl Alveo Best Helmet;<br> Petzl Alveo Vent Helmet;<br> Petzl Vertex Best Helmet;<br> Petzl Vertex Vent Helmet; Petzl Vertex ST Helmet; Petzl Pixa 3; Petzl Pixa 3R.