D.I.D is a Japanese manufacturer of high-performance transmission parts that is renowned worldwide for the quality of its chains & chain kits. Closely involved in competitive racing, the brand also supplies OEM parts for numerous machines. The ERV7 chain is an improvement on the ERV3 which was introduces more than a decade now! * Stronger inner plates, resulting in a 3% higher tensile strength * Greater chain life, which is increased by 13% due to material upgrades with the patented X-Ring seal * The ERV7 will be slightly heavier than the ERV3 Article: D.I.D 520ERV7 X-Ring Drive Chain 520