There are actually two types of links alternating in the bush roller chain. The initial type is internal links, having two inner plates held with each other by two sleeves or bushings where rotate two rollers. Inner links alternate with the second type, the external links, consisting of two external plates held together by pins passing through the bushings of the inner links. The “bushingless” roller chain is similar in procedure though not in structure; instead of individual bushings or sleeves holding the inner plates collectively, the plate includes a tube stamped into it protruding from the hole which serves the same purpose. This has the advantage of removing one part of assembly of the chain.
The roller chain design reduces Stainless Steel Chain friction compared to simpler designs, leading to higher efficiency and less wear. The initial power transmission chain varieties lacked rollers and bushings, with both inner and outer plates held by pins which straight contacted the sprocket teeth; however this configuration exhibited extremely 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 moving through bushings or sleeves connecting the internal plates. This distributed the wear over 
a larger area; however the the teeth of the sprockets still wore more rapidly than is attractive, from the sliding friction against the bushings. The addition of rollers surrounding the bushing sleeves of the chain and provided rolling contact with the teeth of the sprockets resulting in excellent resistance to put on of both sprockets and chain as well. There is even very low friction, so long as the chain is definitely sufficiently lubricated. Constant, clean, lubrication of roller chains is certainly of main importance for efficient operation and also correct tensioning.