Acavallo Arena AluPro StirrupPatented side opening stirrup with a unique HiFLex stress activated locking & release mechanism with big opening in case of emergency. This stirrup is comprehensively tested and safety certified by TUVRheinland in Germany and has a reliable “one click” reengagement of the stirrup locking and release mechanism once triggered.The inner stirrup arm and footplate constructed of continuous integrated metal.The stirrup bow is made of aluminum, while the opening arm is made of a special polyamide material. The stirrup pad is made of polyamide, too, and the tread is fabricated from stainless steel.