Cross-country ski bindings have to do slightly different jobs on different kinds of ski.
Touring bindings are made for ease of use in classical technique. Classical refers to the walking-type motion also called the diagonal stride. Modern system bindings usually offer the tourist the choice to step in without having to manually open and close the binding.
Racing bindings operate manually. This helps make the binding a little lighter and eliminates the risk that someone else’s pole will punch you out of your automatic binding in the melee of a mass start. The flexors may be more firmly anchored for more precise handling. Sport tourists on lighter gear will appreciate that.
Among racing bindings there are two types, classical and skate. There are also two types of skate binding, the flexor style and the Salomon Pilot, using a spring-loaded lever that attaches underneath the boot sole rather than an elastic flexor at the toe.
The wider the ski, the wider the attachment of the binding should be. This has led to back-country versions of both the Rottefella NNN and Salomon Profil system. They use a heavier, wider attachment bar at the toe of the boot. Both come in manual or automatic versions.
Back-country is a bit inaccurate, since these bindings are best used on heavier touring skis in more civilized settings.
The best binding for real back-country is the heavy version of good old 75 millimeter, especially if you like to find little private hideaways to do a few turns. This is not the flimsy old 3-pin of the 1970s touring boom, it’s stronger, adapted to a thicker boot sole.
The BC system binding works well on touring skis from 60 mm to just over 70 in width. Don’t bother to trudge around on a wider ski than that unless you’re looking for some turns or breaking trail in deep snow, both places where 75 mm is far superior.