Army genuine issue Improved Hot Weather Combat Uniform (IHWCU) Jacket. OCP pattern and designed for use in hot, extreme hot, and wet weather environments. These improved hot weather jackets are breathable, fast-drying, and lightweight. Made from a nylon/cotton blend. Permethrin treated. NSN numbers include 8415016707966, 8415016707984, 8415016708106 and 8415016708129.