There are actually two types of links alternating in the bush roller chain. The 1st type is internal links, having two inner plates held together by two sleeves or bushings upon which rotate two rollers. Internal links alternate with the second type, the outer links, consisting of two outer plates held collectively by pins passing through the bushings of the internal links. The “bushingless” roller chain is similar in procedure though not in structure; instead of separate bushings or sleeves holding the inner plates jointly, the plate has a tube stamped into it protruding from the hole which serves the same purpose. It has the benefit of removing one step in Conveyor Chain assembly of the chain.
The roller chain design reduces friction in comparison to simpler designs, resulting in higher efficiency and less wear. The original power transmission chain types lacked rollers and bushings, with both inner and external plates held by pins which directly contacted the sprocket tooth; however this configuration exhibited extremely rapid use of both the sprocket tooth, 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 linking the inner plates. This distributed the use over a larger area; however the teeth of the sprockets still wore more rapidly than is appealing, from the sliding friction against the bushings. The addition of rollers surrounding the bushing sleeves of the chain and supplied rolling contact with one’s teeth of the sprockets resulting in excellent resistance to wear of both sprockets and chain aswell. There is even suprisingly low friction, so long as the chain is certainly sufficiently lubricated. Continuous, clean, lubrication of roller chains is usually of primary importance for efficient procedure in addition to correct tensioning.