Fabri-Valve XS150 High Performance Knife Gate valve features a robust perimeter seal that provides bi-directional bubble tight shutoff. The perimeter seal is double-locked in the valve body to securely retain the perimeter seal in the seal groove even during the most demanding applications. The perimeter seal has shoulders, which mechanically retain (lock) the seal in the seal groove. The tab on the perimeter seal acts as the body joint seal and eliminates the possibility of body joint leakage caused by pipe stresses. The tab also helps retain the perimeter seal in the seal groove (secondary lock). The seal groove is specially designed to prevent seal pull-out but also allows the seal to move and prevent over-compression.