a cMagnetic aluminum cap can be used for the CTC Combi PAL series autosampler; 20mm headspace crimp top vials. Cat NO Description Size Pack Price. HM-0538 Headspace crimp top 5mL clear vials flat bottom 22.5*38 mm 100/PK 14.62. HM-0538C Headspace crimp top 5mL clear vials flat bottom 22*39.5mm 100/PK 14.62.