Acavallo Arena Alupro Aluminum Safety Stirrups feature a lightweight aluminum stirrup bow and a polyamide opening arm with a unique stress activated locking and release mechanism that provides a less rigid and more comfortable feel. The springing stirrup bow and foot support effictively absorbs and compensates for sudden impacts exerted through the rider's weight while posting, jumping or hacking, while the opening arm releasing in case of an emergency. Product Details: Lightweight Aluminum Stirrup Bow Polyamaide Opening arm Unique, stress-actuated locking and release mechanism located between the lower end of the outer, pivoting stirrup arm and the foot support plate/tread. Polyamide stirrup pad - effectively absorbs and compensates for short-term and sudden impacts exerted through the rider's weight from the top, e. g. during posting, jumping or hacking Stainless Steel tread Easy and reliable “one-click” re-engagement of the stirrup locking and release mechanism once triggered. More comfortable feeling to the rider than conventional stirrups. Provides relief to foot bottoms, ankles, knees and hips Ideal for riders suffering from orthopedic problems.