4" super light air tire. Treaded Scale AirWheels are designed to safely absorb the shock associated with landing large or heavy model airplanes. Available in two styles, Scale Treaded AirWheels sport a modern appearance with longitudinally grooved tires. Scale Balloon AirWheels give a more vintage appearance with smooth tires. If desired, the two-piece hub allows for hidden installation of the wheel collars. Tires inflate using a bicycle pump to a maximum of 1 bar (14 psi).