Muaj ntau ntau hom khoom ncej, xws li ncaj, cylindrical, kauv, convex, thiab concave shafts. Lawv cov duab thiab qhov loj me yog nyob ntawm daim ntawv thov tshwj xeeb thiab cov haujlwm xav tau. Cov khoom lag luam feem ntau yog precision machined los xyuas kom meej qhov smoothness thiab seem raug, cia lawv ua hauj lwm stably ntawm high speeds ntawm kev sib hloov los yog nyob rau hauv siab loads.