Abstract: A valve for controlling fluid flow comprising a valve casing having a passage therethrough, an obturator disposed in the passage, and a stem extending through the casing into the passage, said stem secured to the obturator for pivotal movement therewith. A sealing strip is disposed in a groove in the passage, the sealing strip including: a sealing face for compressing, fluid-tight engagement with the obturator, a pair of oppositely disposed, spaced-apart side faces, each side face having a slot therein, each slot overlapping the other slot without interfering with the other slot, and a base extending between said side faces, the width of said base being greater than the width of either of the slots. Rotation of the obturator to block fluid flow through the passage forces the obturator into compressing engagement with the sealing face and distorts the slots.