1. Cov seem crimping yog hexagonal, thiab muaj peev xwm tiv thaiv kev sib hloov tau zoo dua;
2. Kev sib txuas ntawm ob-nias cov yeeb nkab fittings muab ob lub nplhaib tiv thaiv los txhim kho lub zog rub;
3. Lub ob-nias yeeb nkab haum muaj cov lus qhia kom tsis txhob cov yeeb nkab los ntawm khawb lub nplhaib sealing;
4. Lub nplhaib ob-nias sealing yog tag nrho, uas zoo txhim kho lub neej kev pab cuam ntawm lub nplhaib sealing;
5. Daim npav ob npaug ua rau txoj kev khoov muaj zog, thiab txhim kho kev muaj peev xwm kov yeej kev quab yuam sab nraud ntawm cov kav dej.