Acavallo Arena AluPro StirrupsWe love these stirrups for their unique combination of materials. The stirrup bow is made of aluminum, while the opening arm is made of special polyamide material. The stirrup pad is also made of polyamide, and the tread is fabricated from stainless steel. The AluPro model, in principle, provides the same safety function as the Arena HiFlex but it is based on different materials. MAIN FEATURES Unique, stress actuated locking and release mechanism