This boot comes in a two different fits: Insulated and a Performance fit (how Salewa describes the two versions). The Insulated fit is made on a last which is approximately 4mm wider especially, in the forefoot area, which allows for thicker socks or added wiggle room. The two versions share the same materials and construction. Essentially the Pro Gaiter comes in a regular and wide fit, which is unique to any boot we reviewed.
The Pro Gaiter has a very unique feature built into the sole of the boot. The concept is similar to alpine touring ski boots which have a ski/walk mode. In this case the flexibility of the upper stays the same, but the sole stiffness is adjustable.The sole of the boot adjusts from a fully rigid "climb" mode to a semi-rigid "walk" mode with a half turn of a bolt built into the outside of the heel of the boot. The bolt, which is turned by an allen key, torques a tricam like wedge which pulls a full length metal shank tight, making the boot rigid. When the cam is un-torqued the shank allows the sole to flex. You can easily feel the difference between this boot in walk mode and one in climb mode.