Kas fes kraft ntawv zipper hnab nrog cua valve, nws yog ib qho tsim nyog los tiv thaiv cov khoom los ntawm ya raws, tiv thaiv oxidation, ua kom lub saj tshiab thiab tsis deteriorate.Nyob rau tib lub sijhawm, kas fes thiab tshuaj yej kuj yog cov khoom lag luam siab, thiab lawv cov saj thiab qib yuav tsum tau xav txog hauv ntim.