Joy Kids POLLY Balance Bike for Children Details: 12 inch rubber tire; Steel frame; Sponge saddle; Soft rubber handles; Handbrake; White/pink color; Weight 4.1 kg. We know that choosing the right frame size can be difficult, even for experienced cyclists, the right size depends on the type of bike you choose, your height, the style you approach and last but not least, the preferences you have. The guide above gives you general advice on choosing the right bike, depending on its size.