Castle Men's Fuel Realtree G5 Snowmobile Pants (Medium) It also features Ven-Tex 1.0 windproof, waterproof, breathable coated shell materials. Think of it as an attitude with a zipper! The Fuel G5 is an ultra tough, polyester/nylon shell with 3M Thinsulate Extra Warmth 150 g Insulation to keep you warm.