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. Inner links alternate with the second type, the external links, comprising two outer plates held together by pins passing through the bushings of the inner links. The “bushingless” roller chain is similar in operation though not in building; instead of separate bushings or sleeves holding the inner plates jointly, the plate includes a tube stamped into it protruding from the hole which serves the same purpose. It has the benefit of removing one step in 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 the inner and outer plates held by pins which directly contacted the sprocket tooth; however this configuration exhibited incredibly rapid put on of both sprocket the teeth, and the plates where they pivoted on the pins. This issue 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 greater area; however the the teeth of the sprockets still wore quicker than is attractive, from the sliding friction against the bushings. The addition of rollers encircling the bushing sleeves of the chain and offered rolling Conveyor Chain contact with one’s teeth of the sprockets resulting in excellent resistance to use of both sprockets and chain aswell. There is even very low friction, so long as the chain is definitely sufficiently lubricated. Continuous, clean, lubrication of roller chains is usually of primary importance for efficient operation in addition to correct 
tensioning.