Petzl Back Flex Heel Bails One Size. It allows you to use Petzl crampons with mountaineering or snowboard boots that don't have heel welts. Sold in pairs to equip a pair of crampons. Specifications for Petzl Back Flex Heel Bails: Manufacturer: Petzl Size: One Size Fabric/Material: Polyester Stainless Steel Nylon Weight: 125 g Features of Petzl Back Flex Heel Bails Compatible with LEOPARD LLF LEOPARD FL IRVIS HYBRID IRVIS VASAK SARKEN LYNX and DART crampons with the FIL FLEX FIL FLEX SMALL or FIL FLEX WIDE toe bails Product sold in pairs with fastening straps Package Contents: Petzl Back Flex Heel Bails Petzl U018AA00: Back Flex Heel Bails One Size