Cov paj rwb kawg, cov khoom siv paj rwb no los ntawm cov khoom siv polyurethane, tus neeg sawv cev ua npuas ncauj thiab lwm cov tshuaj ntxiv, nias tus neeg sawv cev rau hauv cov pwm yooj yim cua sov tuaj yeem nias tawm ntawm cov duab sib txawv ntawm daim txhuam cev, nws tsim nyog rau kev hloov tig lub rooj zaum lub ncoo, paj rwb rov qab, kuj tseem muaj cov xov tooj me me ntawm armrest tseem siv los ua tiav paj rwb.
Cov khoom siv ntom ntab yog 55 # ~ 60 #, thiab nws qhov elasticity tau raws li cov qauv hauv tebchaws. Lub elastic hardness ntawm daim txhuam cev tuaj yeem kho raws li nyias qhov chaw ntawm cov khoom. Feem ntau, paj rwb puag yog qhov hnyav nyob rau hauv hardness thiab tuab, tom qab los ntawm paj rwb rov qab thiab hauv ncoo cov paj rwb.