This is a TRE4539 3/8" Round Butyl Tape. Butyl tapes are sticky "ribbon type" sealers used for the installation of all gasket-less windshield & backlights. The tape (also called butyl kits) offer the installer a fast, clean method for installing the glass with instant, powerful adhesions. The sealer has excellent compressibility in both low & high temperatures. These tapes are designed to maintain position, while advoiding direct contact,