Stirrups in the aluminium range are made of a special type of aluminium used in aeronotics. The flex-on stirrup offers sophisticated bending which aborbs shock, with a tread that has a grip or ultra grip surface for better adhesion, optimal stability, and a perfect connection with the mount.
The R&D department has designed the stirrup from a solid block geometry to give it strength and lightness.
Please be aware that these are not safety stirrups. If you would like safety stirrups please see Safe-on stirrups here