ProTaper – Chain Links & Tools, including Pro Series Forged 520 racing and slim O-ring chain links, 520XRC master links, 520MX1 and 428MX1 Gold Series master links and 415MX master links, exists for one reason: the connection point is the weakest link in any drive system, and it deserves the right part. Sizing a chain to a bike means breaking it and rejoining it, and the master link you use there sees the same shock loads as the rest of the chain every time the clutch comes out. These links are matched to their parent chains rather than treated as generic spares, so the 520XRC, 520MX1 Gold Series, 428MX1 and 415MX options all pair with the correct pitch and plate thickness. The Pro Series Forged racing and slim O-ring links carry the same forged construction philosophy that makes those chains popular with racers who load the driveline hard off the gate. Keeping a spare link in the toolbox is standard practice for anyone who does their own gearing changes, and it turns a trackside chain problem into a ten-minute fix rather than a lost moto. Correct link choice also keeps sprocket wear even across the whole run.