Chainwheel

Also called a front sprocket. Comes in varying tooth counts. The tooth count will effect how hard or easy the bike pedals (more= harder, less= easier). The center whole can vary in size, some are smaller not intended for 1 piece cranks but the hole can be filed bigger to fit. Chainwheels also come in varying widths. 1/8″ is typical for a single speed or internal gear bike. The smaller 3/32″ is used for multispeed (derailer) bikes. The bigger 3/16″ require a big heavy duty chain and are made for bmx/freestyle bikes.