The N-Ferno 6808ZI Zippered Winter Beanie Hat provides warmth for mild to cold, as well as lightweight protection from bumps, scrapes, bruises and other minor head injuries. Wear alone as a skull cap hat or open the top zippered compartment to add the Skullerz 8943F(X) Universal Bump Cap Insert (included) for work in cramped spaces. Also compatible with Skullerz 8945 Universal Bump Cap Insert (not included) and Skullerz 8945F(X) Universal Bump Cap Insert with Extra Ven