This is a A-RC40M Metric Roller Chain PN: RC40MMain Description As Following : A-RC40M Metric Roller Chain P.N: RC40M B1: 5/16" / 7.75 MMD1: 8.51 MMD2: 4.45 MMDIN: 08 B -1Length: 16'P: 1/2" / 12.7 MM Crossed From: 08B MISCELLANEOUS Found in Section & Models : Chains/ Sprockets/ Pulleys/ Hubs > Metric Roller Chains and Attachment Links, (Miscellaneous) (UNDEFINED): SEVERAL Associated Items : A-CCL1112, A-CL40M, A-OL40M, A-5A1 Also This is An Aftermarket Product And : DIN: 08 B -1 Length: 16' Pin Diameter: 4.45 MM Pitch: 1/2" / 12.7 MM Width: 5/16" / 7.75 MM