Titanium captive adjustment bolts ( 10mm ) Steel axle bolt backing plate is cut to insert into the axle which means you never have to carry an Allen wrench again to remove your axle. All you need is a 17mm wrench Captive adjustment bolt design means when you turn the bolt the axle blocks move forwards and backwards keeping the block tight to the adjustment bolt so there is no play between bolt and the blocks and allows for very precise adjustments One block stays in place and will not fall out when you remove the axleWorks with OEM axle and Warp 9 Titanium