There are two types of links alternating in the bush roller chain. The initial type is internal links, having two internal plates held collectively by two sleeves or bushings upon which rotate two rollers. Internal links alternate with the next type, the external links, comprising two external plates held jointly by pins passing through the bushings 
of the internal links. The “bushingless” roller chain is similar in operation though not in construction; instead of individual bushings or sleeves holding the inner plates together, the plate includes a tube stamped into 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, resulting in higher efficiency and less wear. The initial power transmission chain varieties lacked rollers and bushings, with both inner and external plates kept by pins which straight contacted the sprocket tooth; nevertheless this configuration exhibited extremely rapid use of both sprocket the teeth, and the plates where they pivoted on the pins. This problem was partially solved by the development of bushed chains, with the pins keeping the outer plates moving through bushings or sleeves connecting the internal plates. This distributed the put on over a larger area; however the the teeth of the Transmission Chain sprockets still wore more rapidly than is desired, from the sliding friction against the bushings. The addition of rollers encircling the bushing sleeves of the chain and supplied rolling contact with one’s teeth of the sprockets leading to excellent resistance to put on of both sprockets and chain aswell. There is even suprisingly low friction, so long as the chain can be sufficiently lubricated. Constant, clean, lubrication of roller chains is definitely of primary importance for efficient operation as well as correct tensioning.