Gives requirements for flexible polyester (PETP) films coated on one or both sides with polyester, acrylic or epoxide type adhesive for use in fabricating flexible printed wiring. Films coated on only one side are used as a cover-lay or cover-coat in the fabrication of flexible printed wiring. This coverlay or covercoat is also used to provide local support to areas subjected to mechanical or environmental stress. Films coated on both sides are used as bonding films in the fabrication of printed boards.