This is the S3M-351 3mm belt made by Japanese manufacturer Bando and are replacement parts for the ARC A10-series and R12 touring cars.

This belt also suits most other mid-pulley touring cars including the Awesomatix A800R/MMX, Xray X4, T4 '21, T4 '20, Yokomo BD12, BD11, and the Xpress XQ11 and XQ10.