1. Cov khoom siv hauv chav ua noj no muaj tag nrho cov khoom siv ua noj ua haus yooj yim 2. Cov khoom noj khoom haus silicone, muaj kev nyab xeeb thiab noj qab nyob zoo, tiv taus cua sov 3. Lub taub hau silicone thiab tus kov ntoo tau txuas ruaj khov, yuav tsis raug deformed lossis tawg, thiab tus kov ntoo du yog qhov yooj yim tuav, tsis plam thiab tiv thaiv kev kub hnyiab