The Altra Instinct 4.5 is designed for versatility – after all, in order for you to trust your instincts, you need to be able to handle whatever challenges come your way. It's a 9.8-ounce shoe that uses A-Bound cushioning and InnerFlex grooves to keep you comfortable yet flexible and responsive. The upper is made of engineered mesh, so it offers great breathability, but it won't offer much protection on wet days.