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 where rotate two rollers. Internal links alternate with the next type, the outer links, comprising two external plates held together by pins passing through the bushings of the internal links. The “bushingless” roller chain is comparable in operation though not in structure; instead of separate bushings or sleeves keeping the inner plates with each other, the plate includes a tube stamped into it protruding from the hole which serves the same purpose. This has the advantage of removing one part of assembly of the chain.
The roller chain design reduces friction compared 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 straight contacted the sprocket the teeth; 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 holding the outer plates passing through bushings or sleeves connecting the inner plates. This distributed the use over a greater area; however the teeth of the sprockets still wore quicker than is desired, 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 Leaf Chain excellent resistance to wear of both sprockets and chain as well. There is even suprisingly low friction, so long as the chain can be sufficiently lubricated. Continuous, clean, lubrication of roller chains is certainly of main importance for efficient procedure and also correct tensioning.