There are actually two types of links alternating in the bush roller chain. The 1st type is internal links, having two internal plates held together by two sleeves or bushings where rotate two rollers. Inner links alternate with the next type, the outer links, comprising two external 
plates held together by pins passing through the bushings of the inner links. The “bushingless” roller chain is comparable in procedure though not in structure; instead of individual bushings or sleeves keeping the inner plates with each other, the plate has a tube stamped into it protruding from the hole which serves the same purpose. This has the benefit 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 external plates held by pins which straight contacted the sprocket the teeth; nevertheless this configuration exhibited incredibly rapid use of both sprocket the teeth, and the plates where they pivoted on the pins. This problem was partially solved by the advancement of bushed chains, with the pins keeping the outer plates passing through bushings or sleeves connecting the internal plates. This distributed the wear over a greater area; however the the teeth of the sprockets still wore more rapidly than is appealing, from the sliding friction against the bushings. The addition of rollers encircling the bushing sleeves of the chain and offered rolling contact with one’s teeth of the sprockets leading to Drive Chain excellent resistance to use of both sprockets and chain aswell. There is even suprisingly low friction, provided that the chain is usually sufficiently lubricated. Constant, clean, lubrication of roller chains is usually of main importance for efficient operation and also correct tensioning.