D623504433 / 3504433 LIFELINE ULTRA LOCK SRL 20' OF Ultra-Lok® Self-Retracting Lifeline Made of lightweight and very durable materials, the patented Ultra-Lok® lifeline comes complete with a glass-filled polyurethane housing, a 3/16" wire rope lifeline, and aluminum side plates. Lifeline also features anti-ratcheting twin-disc brake system, audio indicator, self-locking swivel snap hook, and a swiveling anchorage loop to keep the lifeline from twisting.