A type of ski binding system called New Nordic Norm. NNN boots feature a metal rod mounted in the toe that clips into a matching slot in NNN bindings. This system is available in two, non-interchangeable variations: NNN and NNN-BC (New Nordic Norm Backcountry). NNN-BC boots have a thicker rod and are only compatible with NNN-BC bindings. NNN boots are only compatible with NNN bindings.