Sil-Gap 1000 Butter Grade Silicone Sealant is a thick, flexible liquid membrane that is a dispersion of 100% silicone rubber. It is designed to seal abnormal roof penetrations as well as gaping holes that cannot be covered with standard sprayers or rollers. Sil-Gap 1000 features low odor, ease of application, fast moisture cure, and superior adhesion to a variety of substrates.