There are two types of links alternating in the bush roller chain. The initial type is 
inner links, having two inner plates held together by two sleeves or bushings where rotate two rollers. Internal links alternate with the next type, the external links, comprising two outer plates held with each other by pins passing through the bushings of the inner links. The “bushingless” roller chain is comparable in operation though not in Auto Chain building; instead of individual bushings or sleeves keeping the inner plates collectively, the plate has a tube stamped involved with it protruding from the hole which serves the same purpose. This has the benefit of removing one part of 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 inner and outer plates kept by pins which straight contacted the sprocket tooth; however this configuration exhibited incredibly rapid wear of both the 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 holding the outer plates passing through bushings or sleeves linking the internal plates. This distributed the use over a larger area; however the the teeth of the sprockets still wore quicker than is desired, from the sliding friction against the bushings. The addition of rollers around 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 aswell. There is even suprisingly low friction, as long as the chain is usually sufficiently lubricated. Continuous, clean, lubrication of roller chains can be of major importance for efficient operation and also correct tensioning.