Englin's Presents the "Isotherm" from Merrell Shoes. Enjoy all the cold-weather activities you love in the Merrell "Isotherm Zip Waterproof" boot. This men's outdoor boot has a full grain leather upper with a front zip, bellows tongue and a waterproof, breathable membrane. Primaloft insulation and an ActiveHeat insole deliver reliable, continuous warmth. The Vibram outsole of the Merrell "Isotherm Zip Waterproof" boot provides superior traction and durability.