Fisherbrand™ 20mm Crimp Seal, Silver, Headspace Cap (Pressure release cap), Assembled septum. Pressure release seals (Aluminum-PR) are designed to open when internal pressure exceeds 3.0±0.5bar. Fisherbrand™ Screw Neck Vial, 13-425 Thread, Glass, 4mL. Ideal for storage purposes when used with closed top screw seals.