There are two types of links alternating in the bush roller chain. The 1st type is inner links, having two inner plates held together by two sleeves or bushings upon which rotate two rollers. Internal links alternate with the second type, the external links, consisting 
of two external plates held collectively by pins passing Leaf Chain through the bushings of the internal links. The “bushingless” roller chain is similar in procedure though not in structure; instead of separate bushings or sleeves holding the inner plates collectively, the plate has a tube stamped involved with it protruding from the hole which serves the same purpose. It has the advantage of removing one step in assembly of the chain.
The roller chain design reduces friction in comparison to simpler designs, leading to higher efficiency and less wear. The initial power transmission chain types lacked rollers and bushings, with both the inner and outer plates held by pins which straight contacted the sprocket the teeth; nevertheless this configuration exhibited incredibly rapid use of both the sprocket tooth, and the plates where they pivoted on the pins. This issue was partially solved by the development of bushed chains, with the pins holding the outer plates passing through bushings or sleeves linking the internal plates. This distributed the use over a larger area; however the teeth of the sprockets still wore more rapidly than is desired, from the sliding friction against the bushings. The addition of rollers surrounding the bushing sleeves of the chain and offered rolling contact with one’s teeth of the sprockets resulting in excellent resistance to put on of both sprockets and chain aswell. There is even very low friction, provided that the chain can be sufficiently lubricated. Constant, clean, lubrication of roller chains is usually of main importance for efficient procedure as well as correct tensioning.