... ,XL,L,H,XH,XXH,XXL,SL9,SL12,SL,HTD:3M,5M,8M,14M,20M AND SO ON2. Metric System: T ... -type series(T2.5,T5,T10,T20)3. HTD type(3M,5M,8M,14M)4. STPD/STS type(S2M,S3M,S4 ... .7. Surface treatment:black oxdizing,phosphating,anodize,zinc-plating Timing belt pulley