The Thumper 20R8 is a great first 'grown up bike' for your young teen. The 8 speed Shimano Rapidfire trigger Shifter makes learning to shift a breeze, front and rear caliper brakes have custom sized levers for young hands and the safety reflectors and bell ensures your child can be seen and heard. Frame: Butted Alloy Frame, Low Gravity Concept Design, CRM Forks, seat height 23.2 - 28.7 inches Wheels: Reinforced Alloy Wheels with Machined Braking surface for Greater Power, lightweight Micro Knobby Design tires with Tough Tubes Brakes: Alloy Tektro Front & Rear Calibrated V brakes with Max Power Alloy Tektro Custom Sized Levers Cockpit: Adjustable, Comfort Midi Deluxe saddle, Custom Width Low Rise V-Bar handlebars and Shimano Rapidfire 8 Speed Trigger Shifter Gears Extras Included: Safety reflector, bell, kickstand