Roj twj tso kua mis yog ib hom lub teeb thiab compact twj tso kua mis, muaj peb pawg ntawm in-line hom, tis hom thiab ib hom. Cov roj twj tso kua mis yuav tsum muaj lub zog los ua haujlwm, thiab lub camshaft nyob rau hauv nws yog tsav los ntawm lub cav crankshaft iav.
Lub twj tso kua mis roj muaj ib lub qhov rooj uas ua los ntawm cov khoom siv aluminium thiab cov pwm txav mus rau hauv lub thawv yog muab, qhov twg cov pwm txav tau tsim tsawg kawg hauv ib feem ntawm cov khoom siv sintable uas muaj tsawg kawg yog ib qho austenitic hlau-raws li alloy. Lub molded ib feem, uas yog ua los ntawm ib tug sintable khoom, muaj ib tug coefficient ntawm thermal expansion ntawm tsawg kawg yog 60 feem pua ntawm cov coefficient ntawm thermal expansion ntawm lub plhaub.