Txawm hais tias peb txhua tus paub qhov tsis kub kub tshuab pwm, ntau tus neeg tsis paub yuav ua li cas pwm no. Cia kuv qhia rau koj. Ua ntej, muaj ntau hom cib tshuab pwm, xws li hollow cib pwm, txheem cib pwm, xim cib pwm thiab heterosexual pwm. Los ntawm cov khoom taw tes ntawm view, muaj yeej peb hom. Thawj yog cov pwm ua los ntawm cov hlau zoo tib yam, uas tau muab faib ua pwm sab sauv thiab qis pwm, Qhov thib ob yog ua los ntawm No. 15 manganese steel, xws li cov saw hniav rau txiav marble. Qhov thib peb yog zinc carbon pwm, uas yog sib npaug rau No. 65 manganese steel. Qhov siab dua ntawm manganese daim ntawv lo yog, qhov nyuaj ntawm cov txheeb ze hnav-tiv taus lub zog yog, tab sis nws kuj yog ib qho yooj yim rau nkig. Qhov no yog vim li cas cov pwm feem ntau nyob rau hauv lub xeev zoo tshaj plaws thaum cov manganese tsuas yog 65. Txawm hais tias cov ntawv siab npaum li cas, nws muaj zog, tab sis nws yooj yim tawg. Yog tias daim ntawv lo qis, nws tsis muaj zog thiab tsis hnav-resistant. Qhov no yog ib qho kev qhia luv luv rau pwm.