Attwood's multi-layer primer bulbs provide the absolute best combination of performance, reliability, safety and compliance to ensure your experience on the water is easier and safer to enjoy. Their exclusive three-layer design resists collapsing and hardening and ensures high output in temperatures ranging from 18 degrees F to 122 degrees F. Includes high-effieciency check valves with Vitron O-rings for improved sealing. Assembled with the same components as Mercury and Quicksilver.