A bicycle chain is a roller chain that transfers power from the pedals to the drive-wheel of a bicycle, thus propelling it. Most bicycle chains are made from plain carbon or alloy steel, but some are nickel-plated to prevent rust, or simply for aesthetics. Nickel also confers a measure of self-lubrication to a chain's moving parts. Chains will vary in width depending on the amount of gears you have, most are 3/32 inch for use with geared systems and then come in 'speeds' which needs to matched to the cassette, ie a 10 speed cassette will need a 10 speed chain and so on. Track bikes or single speeds often run 1/8 inch rings so will need a 1/8 inch chain as well, these will have larger plates to aid stopping on a fixed wheel, which can add extra stress to a chain.