This mitered inside corner is precision molded in high-density polyurethane, one of today's most versatile high-performance materials. Polyurethane includes a unique closed cell structure, which results in non-porous and highly moisture resistant products. The mitered inside corner remains free of warping, staining and decay. It is also pre-primed. This mitered inside corner is designed for use with the Massive Crown E-Vent profile (EV580). Extend the life of your roof and adorn your home in style with a finely crafted E-Vent system. E-Vents blend with traditional materials and trim while complimenting the home exterior overall. Mitered inside and outside corners result in perfectly angled corners every time.