You can bundle up under your waders, but sometimes it isn't just the water that's cold. The Simms MidCurrent Hooded Jacket helps protect your top half from the cold air around you. PrimaLoft Cross Core Gold uses Aerogels--also used by astronauts--to trap in body heat without weighing you down. Mapped insulation emphasizes warmth for your core, head, and neck, while allows for additional airflow at the arms where you need it. The Toray Airstatic material is lightweight and offers controlled air permeability to let air in but keep wind out, while a DWR treatment protects you from splashing water and light precipitation.