Frame bindings are compatible with any alpine ski boot. A ski binding is a device that connects a ski boot to the ski. During the 2000s, Denny re-entered the ski boot market with the Apex ski boot. Under the new ownership, the company continued development of the classic front-opening ski boot design. The new four-buckle system is largely identical to any modern downhill ski boot. This led to the Rosemount ski boot of 1965, one of the first all-synthetic designs. The Flexon was a downhill ski boot introduced by Raichle in the winter of 1980/81.