RaceFace Atlas Mountain Bike Stem with 50x35mm Clamp, Black, 1 1/8-Inch 6061-T6 aluminum Four bolt bar clamp holds bar securely in position, interlocking U-Shaped Handlebar Clamp Geometry Faceplate eliminates "stress risers" which cause your bar to bend or break Opposing bolts on steer tube clamp provides extreme clamping power while reducing stress on the steer tube Weight: 141g (35mm), 160g (50mm), 181g (65mm)