The Trango Tower was first introduced last year to replace the Trango S Evo. It comes in at around a B2 rating. The Trango Tower Extreme GTX is one of the lightest B3 boots ever made. The uppers remain largely the same, however the sole is much stiffer. The sole is not 100% stiff which allows for greater comfort but it is stiff enough to take a fully automatic crampon. The sole remains the same although the mid-sole is much stiffer. The neoprene cuff extends slightly higher.