It is important for safety that the bike you choose is the right size for the intended rider. Correct fit ensures your new bike will be safe, comfortable, and will handle correctly. Be careful not to select a bike that may be too big or too small for the rider. The rider must be able to stand astride the top frame bar of the bike with both feet flat on the ground and have at least 25mm clearance (50mm for MTBs).
The rider must also be able to comfortably reach the pedals and operate all the handlebar-mounted controls while in a seated riding position.