This is PKT's Kid Kart Brake Rotor. It measures 160mm (6.3in) in diameter and is 3mm (.12in) thick or 2.3mm (.09in) for the super lightweight. There finally is an alternative to the heavy oem rotors. The light weight version of the rotor weights 9 ounces (7 ounces for the super lightweight) and is designed for quick heat dissipation. The rotor fits our current line of brake rotor hubs in 25mm, 30mm & 1-1/4" axle sizes. 6mm key is required. It is available in the light weight version or the new super light weight version (+$10.00).