Binding, boot, and ski compatibility can feel confusing at first, but have no fear. The three primary Nordic touring binding options are a traditional three-pin binding, SNS binding system (or XA for Nordic touring), and the NNN/NIS BC (New Nordic Norm Backcountry) binding, which uses a small but strong toe clamp to secure your boot. Both of these options make it easy to control your skis, and are more rugged than standard Nordic skiing bindings. The three-pin binding is easy to repair but can be too wide for groomed Nordic track, while the NNN/NIS BC binding is available in both automatic step-in and manual models—both of which require NNN/NIS compatible boots.
NNN/NIS BC bindings use a small clamp that secures a bar at the toe of your boot, while three-pin bindings use metal pins and a toe bail for security. SNS (similar to NNN/NIS) uses a the smallest toe bar and a modified binding plate with a large ridge that runs from toe to heel to help guide the boot.
Three-pin bindings work with traditional three-pin duckbill boots, while NNN/NIS BC bindings work with NNN BC-compatible and NIS boots. SNS bindings require SNS boots and are not compatible with NNN/NIS.
You can mount three-pin, SNS, and NNN/NIS BC bindings on any flat Nordic ski. Be sure to choose a plate-compatible binding if your Nordic ski includes a binding mounting plate (attached to the ski topsheet).