These quick release skewers work on an internal cam. This is the original and best design for a wheel skewer. Most bikes today are fitted with external cam systems and are prone to slipping, especially used on semi-horizonal or track dropouts. Campagnolo designed the internal cam system and it is still the best there is.
The acorn nut (the one without the lever) is alloy, but it has a chrome steel face pressed on for better grip and durability. It also has a nylon insert to prevent loosening. The other end also features an alloy housing; the lever and cam, however, are chromed steel, so they won't break when you over-tighten them.
For 130-135mm rear spacing, 100mm front. Sold as pairs, front and rear, only. 135g per pair.