35 degree stem with strong 6061 T6 aluminium 3D forged body. Specification & Features of BBB Highrise OS Ahead Stem. Material: 6061 T6 aluminium. Construction: 3D forged. For 1. 18" steerers. Bar bore diameter: 31. 8mm. Angle: 35º. Stainless steel bolts. Weight: 148g (based on mid-sized stem). BBB Highrise OS Ahead Stem is perfect for:. Mountain Bike.