Aircast AirSelect Walker (Standard) The Standard walking boot offers a moderate level of support and Aircast's quality, effectiveness and comfort in an economical model. The main indications for the Standard are fracture of the foot/ankle/lower leg, severe ankle sprain and post-operative immobilization. It has a semi-rigid shell that helps support the leg while providing protection. SoftStrike technology absorbs and dissipates shock, while the light weight of the boot encourages a continuation of everyday activities. Boot Height: - Large - 17.4-inch