The Aerobar Riser kit is designed to help deliver your perfect bike fit with your Profile Design aerobars Find comfort and performance by getting your fit correct Wind tunnel testing has also shown that increasing the stack of the armrests with the riser kit rather than steerer tube spacers reduces overall drag Increments of 20 mm to 70 mm are available Each riser is forged and machined alloy The bolts are marine grade steel to withstand the forces associated with stacking risers Compatibility: Sonic Ergo (35a, 45/25a and 50a), Supersonic Ergo (35a, 45/25a and 50a), T Carbon Series, T Aluminium Series Aerobars