The N-Ferno 6802Z Zippered Stairs Hat provides warmth from extreme cold, as well as the option for lightweight protection from bumps, scrapes, bruises and other minor head injuries. Wear alone as a classic aviator hat or open the top zippered compartment to add the Skullerz 8945 Universal Bump Cap Insert, Skullerz 8945F(x) Universal Bump Cap Insert with Extra Venting or Skullerz 8943F(x) Hinged Universal Bump Cap Insert (sold separately) for work in cramped spaces.