Adjustment clamps are used to adjust bearing preload on Chris King hubs. Fits ONLY Chris King ISO (serial numbers starting with 161) ISO-B (serial numbers starting with 851) rear hubs equipped with Twin Bearing or Gen 4 axle systems Not for ISO/ISO-B rear hubs equipped with Needle Bearing systems If you have a Needle Bearing equipped rear hub, you will need the High Profile or Low Profile Adjusting Clamp PHB712, PHB712B