Product Description DMT insulation backing on 73-76 A body AC heater boxes. Insulates between heater / AC box and firewall. NOTE: This piece is already included in the AC heater box rebuild kit. 1973 73 1974 74 1975 75 1976 76 Dart, Demon, Duster, Scamp, Valiant AC heater boxes Materials3/4" matte faced yellow fiberglass insulation. Exact same shape as OEM ShippingFirst Class Mail. We combine shipping.