A permanent stressed end cap for a post tensioned concrete member includes a grout retention feature adapted to retain a filler material within a void formed by a pocket former. The grout retention feature may be a generally knob or mushroom shaped, hex-headed, or square body extending from the cap. The grout retention feature may include one or more protrusions extending from the exterior of the cap. The grout retention feature may include one or more surface textures on the exterior of the cap.