Apex Stems The Renthal Apex stem covers all sectors of mountain bike. Light enough for XC racing, stiff and strong enough for a 780mm handlebar. The Renthal Apex stem features our unique new clamping system. This allows much of the stem body material to be removed, whilst retaining the strength and stiffness demanded by modern, wide handlebars. The clamps are inserted over the small diameter section of the handlebar and slid into the centre, giving a 240deg wrap of the handlebar. The Renthal Apex construction comprises a fully CNC machined 2014 aluminium body and 7075 aluminium clamps.