Permanent Ink: Cov cim nrog tus cwj mem mus tas li, zoo li lub npe cuam tshuam, yog qhov ruaj khov.Nyob rau hauv tus cwj mem muaj cov tshuaj hu ua resin uas ua rau tus number case stick thaum nws siv.Cov cim tas mus li yog cov dej tsis muaj dej thiab feem ntau sau rau ntawm ntau qhov chaw.Tus cwj mem mus tas li yog ib hom cwj mem siv los sau rau ntawm ntau qhov chaw xws li duab los qhia, ntawv, yas, thiab lwm yam.Tus cwj mem mus tas li feem ntau yog roj lossis cawv.Tsis tas li ntawd, tus number case yog dej-resistant.