.METRIAL: Center nut : 304 stenless steel (Corrosion prevention, prevent bolt abrasion)
Roller : Aluminium Alloy (Light)
.The hook roller alone in fitted, it is no need a lot of orginal parts(long bolt, bushing, washer, nut...in Brompton R version)
.Insert a rubber washer between the two Parts(center bolt, Roller) and the bolt will not disengage during riding.
.5mm, 6mm size Choice
.Black; Silver; Titanium; Gold Color Choice