Pro Taper ATAC Stem The Pro Taper ATAC Stem is back! This is a proper stem for any serious and dedicated enduro or gravity rider. The Pro Taper ATAC Stem is one of the oldest and well-known high-end stems in the mountain riding game. This time around the Pro Taper ATAC Stem comes upgarded with titanium hardware and a fresh laser etched finish. It also comes in a multitude of sizes to accommodate sizing preferences and is designed to fit a 31. 8mm clamp diameter. Features Weight: 90g Length: 50/60/70/80/90/100Clamp Diameter: 31. 8mm Rise: +/-5 degrees Hardware: titanium | Protaper | Atac Stem Black/ | White | 50Mm | Aluminum