I-cap yenziwa nge-aluminium. I-aluminium isetshenziswa kakhulu ngenxa yezakhiwo zayo ezinhle kakhulu zokubekwa uphawu nokumelana nokugqwala. I-Septa iyingxenye ebucayi ye-cap futhi yenziwe nge-silicone noma i-PTFE (polytetrafluoroethlelene). Kubekwa ngaphakathi kwi-cap futhi kusebenza njengesithiyo phakathi kwesampula kanye nemvelo yangaphandle. I-cap inomklamo ophezulu we-crimp, okusho ukuthi inganamathiselwa ngokuphephile ku-vial ngokusebenzisa ithuluzi lokukhohlisa. Le nqubo ifaka ukugoqa i-cap ezungeze intamo ye-vial, yakha uphawu oluvikelekile nolubonakalayo. Lezi zimbobo ezinama-septa zinikeza isithiyo esisebenzayo ekungcoleni, ukuhwamuka, kanye nezinguquko ekwakhiweni kwesampula, ukuqinisekisa ukuthi isampula lihlala lizinzile futhi lithembekile ngokuhlaziywa.