This is the Pro Atherton 31.8mm Downhill CNC Stem. A fully CNC machined threadless DH stem. Made from Fully CNC machined threadless DH stem Strong and light 7050 aluminium material. Durable and strong 5mm Allen key bolts. The design of this item ensures it offers optimum rigidity. Suitable for 1 1/8” steerers and 31.8mm handlebars.