Hedgehog best fit for riders with an inseam of 17" to 21". First time riders feel safest with their bottom on the saddle and their feet flat on the ground. That's how a child with an 18" inseam will fit the Hedgehog with the seat post dropped as low as possible. Once kids get more comfortable on two wheels, they'll want to sit on the saddle with the balls of their feet on the ground. Thus, a confident rider with a 17" inseam and a first-time rider with a 19" inseam will each ride with about the same seat height.