Best kids bike out there - Frog bikes are built specifically for children so they are incredibly light and easy to use. In terms of the spec, it has Tektro brakes, 8-speed Shimano easy-change thumb shifters and 8 speed cassette hub. Suitable for minimum inside leg of 55cm (around 6-9 years old), it has 20" wheels. The all-aluminium bike has a high quality frame, easily adjusted saddle height and a crank length of 114mm. My son has absolutely loved it and we're selling this one to get the next size up. The bike is in excellent.