Roof Flashing NeopreneDescription Our Roof Flashing Neoprene is used to prevent water from seeping through a roof, this is for use with copper, cast iron, galvanized, or plastic pipe. Constructed from non fading, non cracking, rigid black thermoplastic for a roof pitch of 0 45 degrees or up to a 12 12 roof. The flashings have a self sealing collar, which slides over pipe tight and easily. This product does not require caulking and is not for hot mopped or built up roofs.