4016 #40 Economy Chain Half Link for the 40-1R-10 Economy #35 Chain. Do not use this half-link with any performance chain. 

Do not use this half-link with any performance chain. 

The half link is what you think; it’s half the chain link. The half link allows you to fine-tune the length of your chain better when there is limited space or range the chain has to get its required length. However, if using this in a racing application, we highly recommend using a chain breaker tool to make permanent chain lengths. Otherwise, the master link may come apart.