The Proper Rear Hub Guard protects your hub and spokes from grind damage on your none drive side and helps to maintain a consistent grind, especially over kinks. The Proper rear hubguards are CNC'd from 7075 alloy for maximum durability. This guard screws on (in place of your none drive side cone nut) so there is no need to spread your drop outs. This guard will fit all male Proper rear hubs manufactured within the last four years. It will also fit the newer type of female Proper rear hub (with a 14mm axle - as opposed to 10mm axle with a 14mm shim).