Axle system end caps or conversion kits for Industry Nine hubs For non-boost Hydra 6-bolt front 15x100mm to 20x110mm non-Boost end caps, use XN6155 (IS) International Standard 6-bolt (CL) Center Lock Not compatible with 20mm axle front hubs with BB61805 bearings TECH SPECS table{border-collapse:collapse;width:100%;} td{text-align:left;padding:8px;font-weight:350;} tr:nth-child(even){background-color:#f2f2f2} th{background-color:#eb212e;color:white;text-align:left;padding:8px;} .desc .specs-heading{font-size:24px;font-weight:600;padding-top:35px;border-top:3px solid #f0f0f0;display:inline-block;border-bottom:4px solid #eb212e;width:142px;margin:0;} Model Hydra 2 Description 15x110mm End Caps