Botas de Travesía Nórdica

Nordic touring boots are similar to walking boots but with a special sole design that allows the boot to be connected to the bindings. There are three types of nordic touring boots, with different sole designs corresponding to the three types of nordic touring bindings, and your boots need to be compatible with your bindings. Nordic Touring boots are warm, waterproof and reasonably light so that you can cover long distances comfortably. While most boots are designed for general nordic touring, there are insulated models with built-in gaiters and double boots for expedition use in extreme conditions. Most bootsd use laces for closure, with some top end boots now using the Boa cable system. For added control when descending some models have external heel supports with either a Velcro strap or a single plastic buckle.
75 mm Boots.
These have the 75 mm telemark standard sole design, with an elongated toe extension or "duckbill" which is 75 mm wide at the front, hence the name. The duckbill sole has three lateral holes into which the three vertical pins of the "3-pin" telemark bindings locate. Some telemark bindings also have cables that connect to the boots via a lever at the heel, and these boots have a rounded slot in the midsole of heel for this. All 75 mm boots use the classic Vibram telemark sole, and these boots can be re-soled by a good cobbler/boot repair centre. The thickness of the sole + midsole can vary between boots, depending upon the stiffness and level of thermal insulation built into the boots, and the closure mechanism of the 3-pin bindings has several positions to cope with this variation in sole thickness.
NNN BC Boots.
These all have a special sole with a lateral metal bar positioned under the toes. This connects to the jaws of the NNN BC bindings, which are beefier versions of cross country track bindings. The sole has a central slot which corresponds to the central ridge on the bindings, providing good boot-binding contact and improving lateral control. While these are excellent boots for skiing, they are less practical if you will doing a lot of walking, since it's possible to damage the metal bar on rough terrain, and the overall design of the sole is less robust for walking than the classic Vibram sole of the 75 mm boots. 
Xplore Boots.
These have a specific sole design created by Rottefella with two spring-loaded pins positioned on each side of the boot toe. These pins connect into the slots of the Xplore bindings and provide friction-free rotation for efficient movement.
The front lever of the bindings presses the pins inwards to exit the bindings. It's a neat system. Xplore boots have a rugged sole that is practical for walking. Xplore boots tend to be a little more expensive than the other boots but this system is rapidly becoming vary popular, especially for use with wider nordic touring skis.