Chain sizes may seem to be made up by a madman, but are actually just code for the pitch, or pin-to-pin distance, expressed in eighths of an inch, and for the inside width of the chain, again in eighths of an inch. A 530 chain has a pitch of 5⁄8 in. (5), and a width of 3⁄8 in. (3.0). A 525 chain has a 5⁄8 in. pitch and is 2.5 eighths wide, or 5⁄16 in. Depending on the displacement of the bike, the chain will come with a clip-type master link or a rivet-type—some replacement chains come with both. The rivet type is best for large-displacement bikes but requires special tools; it’s less convenient but arguably stronger.