18mm 20ml Radius bottom for CTC. Clear 18mm screw, red butyl/ natural PTFE 018-18-6270 18mm Headspace Vial Kits Cap Vial Type Glass Description PartNumber 20mm 20ml Beveled edge, round bottom, crimp Clear 20mm black butyl/grey PTFE - Pharmafix 020-18-6269 20mm 20ml Beveled edge, round bottom, crimp Clear 20mm clear silicone/natural PTFE 020-18-6268