For BOSCH® system chainring.

MATERIAL : Cr-mo steel (ASM 4140) heat treated
SPEC : TRSK-BSH = 0 offset
           TRSK-BSH-OF3 = offset 3mm for OLD 142mm
           TRSK-BSH-OF6 = offset 6mm for OLD 148mm
TEETH : 14T, 15T, 16T, 17T, 18T, 19T, 20T
OPTION : N.E.N finish / ED / BK