DID 520ERV7 G-120 ZB Race X-Ring Drive Chain - GoldDID 520ERV7 G 120 ZB Race X Ring Drive Chain High performance, lightweight, low friction chains designed exclusively for racing Pins for ER chains are put through a special patented heat treatment process that produces a 1. 5 times harder than conventional carbon heat treating Provides the highest wear resistance, tensile strength and impact resistance available ER chain used by top motocross Supercross OEM works teams