Headspace crimp top vial, 20 mL, 23 x 75 mm, clear, flat bottom: Maximum recommended fill volume is ¾ full: Cap: (100/pk) Headspace crimp cap with septa, 20 mm, silver aluminum cap, PTFE/silicone septa. For any headspace applications using a pressure over 45 PSI, use of a safety release cap is strongly recommended to prevent damage