... 4.inner diameter:12mm 5.pitch:12.70 Specificationsindustrial transmission roller chain sprocket MaterialC45,40Cr,20CrMnTi,42CrMo,stainless steel ..... as per your ... 's requirementstandardGB1244-85,DIN8187,8188;ISO/R606Model numberStandard or nonstandard (single duplex and triple)05B,06B,08A,08B,10A,12A,16A ... -win business relations with you in the near future. industrial roller chain sprocket