GenTite Peel & Stick corners are precut to 8.5" to make flashing an inside or outside corner quick and simple. They are composed of uncured EPDM (rubber roofing) laminated to a cured butyl based adhesive tape. Corners are specifically designed to be used in roofing applications. May also be used for small repairs or patches. They are not to be used as T-joint covers. Size: 8.5" (216mm) diameter. Flashing thickness: 0.065" (1.59mm).