The 12eDRIVE (pictured below) is recommended for most 3-5 year olds. The 16eDRIVE is recommended for most 5-7 year olds. The 18eDRIVE is recommended for most 8-10 year olds. The 20eDrive is recommended for most 11-12 year olds.
Each model has 3 different modes/speeds. A low/training mode, medium/standard mode, and high/advanced mode. The 12 and 16 also have a nonpower kick/push mode, which is great for kids learning how to balance!