The single Stainless Steel Rubber Spike Foot from Manfrotto is a spare or replacement part, which is compatible with the MT055XPRO3 and the foot fits tripod legs with a diameter of 22.5mm. Furthermore, when the rubber foot retracts back it exposes a stainless steel spike that is driven into soft ground, stabilizing the tripod on uneven terrain. Also, the foot prevents the tripod from sliding on smooth surfaces.