1.1 This specification covers unsintered extruded films or tapes manufactured from virgin, unpigmented polytetrafluoroethylene, in nominal thickness from 0.025 to 0.51 mm [0.001 to 0.020 in.], and are > 97 % PTFE in composition.1.1.1 The use of This specification covers three types and several grades of unsintered extruded films or tapes manufactured from virgin, unpigmented polytetrafluoroethylene in specified nominal thicknesses. Having different apparent densities, the three types of tapes