Master link

The other plate fits over the ends of the pins and is secured with a spring clip to make the connection, and this type of master link comes closest to being re-usable.

For bicycles with derailleur gears, a special kind of master link has been developed to fit the narrow chains used on closely spaced sprockets.

In this way the pair form a loosely interconnected, closed set, with each master link's pin located in the slot of the other, and the two bushings held captive.

The special pliers have curved ends to accommodate the rollers, and make easy work of even the most difficult removal.

Since a chain on a derailleur-fitted bicycle is reversed for part of its excursion through the drive-train, and because some cogsets have close ramp tolerances, such a link might cause a malfunction if the wrong selection were made.

As a result, some manufacturers of derailleurs (e.g. SRAM) recommend only their own products, and these days package a master link with each new chain that is purchased.

Figure 1: A traditional master link, compatible with straight chainlines and widely spaced sprockets.
Figure 2: Schematic of a modern master link.
Figure 3: A SRAM Powerlink, joining two ends of a chain.
Figure 4: A master link with a slightly raised profile. Note that the embossed arrow should point toward the inside of the chain-loop. Note also the more prominent pin excess.
Figure 5: Master link pliers. They fit over the rollers to take the hard work out of link removal.