This is a A-RC100M Metric Roller Chain PN: RC100MMain Description As Following : A-RC100M Metric Roller Chain P.N: RC100M B1: 3/4" / 19.56 MMD1: 19.05 MMD2: 10.19 MMDIN: 20 B - 1Length: 16'P: 1 1/4" / 31.75 MM Crossed From: 20B MISCELLANEOUS Found in Section & Models : Chains/ Sprockets/ Pulleys/ Hubs > Metric Roller Chains and Attachment Links, (Miscellaneous) (UNDEFINED): SEVERAL Associated Items : A-CCL1112, A-CL100M, A-OL100M, A-5A2 Also This is An Aftermarket Product And : D1: 19.05 MM DIN: 20 B - 1 Length: 16' Pin Diameter: 10.19 MM Pitch: 1 1/4" / 31.75 MM Width: 3/4" / 19.56 MM