One frame covers five stages here: a pedal tricycle for a two year old, a walker for wobbly first steps, a training bike, a balance bike, and a narrow-track two-wheeler. Pedals unbolt in minutes and the rear wheels shift between two track widths, so the bike keeps pace as balance improves. The handlebar sets to four heights for riders 34.5 to 43.5 in tall, and steering stops at 135 degrees to keep the front wheel from folding under. A welded triangle carbon steel frame holds up to 66 lbs, folds fast for the trunk, and meets ASTM and CPSIA requirements.