Timing pulleys (XL,L,H,XH,XXH) HTD Timing pulleys(3M,5M,8M, ... ,T10,T20,AT5,AT10),etc. timing pulley HTD ,Timing pulleys (XL,L,H,XH,XXH) HTD Timing pulleys(3M,5M,8M ... treatment:black oxide,phosphate,anodize and zinc plating. Timing pulleys (XL,L,H,XH,XXH)