These Avid HB Steering Bushings are made of Delrin and offer the kit position bushings as well as the optional offset bushings for the D819RS/E819RS (HBS204568) and D8T/E8T Evo3's (HBS204656). The offset bushings allow you to raise or lower your axle to fine-tune your vehicle. The best rule of thumb for the offset bushings is if you are running lower ride heights then move the axle further away from the a-arm and vice versa, if running higher ride height then lower the axle closer to the a-arm. But feel is different for everyone so we encourage everyone to try both settings to get the feel for them.