I-cap yenziwa nge-aluminium. I-Aluminiyam ihlala isetyenziswa ngenxa yeepropathi zayo ezilungileyo zokulinganisa kunye nokuxhathisa ukusula. I-Septa yinxalenye ebalulekileyo ye-cap kwaye yenziwa nge-silicone okanye i-ptfe (i-ptfe (polytetrafluorookenene). Ibekwe ngaphakathi kwi-cap kwaye isebenza njengomqobo phakathi kwesampulu kunye nendawo yangaphandle. I-cap ine-crust yoyilo oluphezulu, okuthetha ukuba inokuthi iqhotyoshelwe ngokukhuselekileyo kwi-vial ngokusebenzisa isixhobo sokukhusela. Le nkqubo ibandakanya ukuqhekeza i-cap ejikeleze intamo ye-vial, edale itywina eliqinileyo nelibonakalayo. Ezi pikseli ze-Septa zibonelela ngesithintelo esisebenzayo ngokuchasene nongcoliseko, ukuvela, kunye nokuguqula isampulu, kuqinisekisa ukuba isampulu zihlala zizinzile kwaye zithembekile kuhlalutyo.