Single row cylindrical rolleer bearing can be detached, so it is easy to install and take apart. The two bearing rings can use close fit, and the osculatory between the corrected roller and the racewan can reduce the stress concentration. Full cylindrical roller bearing is particularly used to super-heavy load and medium speed cases. Pachingless single and double row bearings are more applicable to jack mechanism. Seperable bearing's two rings can both use close fit so as to install and take apart easily.