Always use the right bar for your boot. Flexible boots need a flexible bar to reduce the stress on the metal parts caused by walking. FLEX BAR: The crampons with either Classic or New Classic bindings now have a flexible regulation bar for improved fit and performance on walking boots. It allows the foot free movement without over-forcing or stressing the bar even over extended use. The flex regulation bars are made of multi-ply stainless steel and work just like a cars suspension springs. Note: the Flex Regulation Bars can be used on all of Grivels crampons. VALTER: new regulation bar that makes changing from one size to a smaller one easy, by simply turning the bar over. The retaining tooth, on touching the crampon, automatically reduces the size offering extremely quick fitting with no tools. Remember that the right crampon becomes the left and visa versa by flipping the bar over. SUPER ASYMMETRIC: The solution that permits a superb fit for the latest generation of asymmetrically curved alpine boots. The points are aligned in the correct position below the foot, with no dangerous overhangs and provide increased efficiency on ice. Available as an optional item, the super-asymmetric bar can be used on all Grivel crampons. G20 and G22: Patented MONO RAIL technology makes a stable platform underfoot. TWIN bar is used for boots with rocker soles. They allow more flex while walking, reducing the stress on the metal parts of the crampon.