There are two types of links alternating in the bush roller chain. The first type is inner links, 
having two internal plates held with each other by two sleeves or bushings upon which rotate two rollers. Internal links alternate with the next type, the outer links, consisting of two external plates held jointly by pins moving 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 together, 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, leading to higher efficiency and less wear. The original power transmission chain types lacked rollers and bushings, with both inner and external plates kept by pins which directly contacted the sprocket tooth; nevertheless this configuration exhibited incredibly rapid use of both the sprocket teeth, and the plates where they pivoted on the pins. This issue was partially solved by the advancement of bushed chains, with the pins keeping the outer plates moving through bushings or sleeves connecting the inner plates. This distributed the use over a larger area; however the tooth of the 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 provided Leaf Chain rolling contact with the teeth of the sprockets leading to excellent resistance to use of both sprockets and chain as well. There is even very low friction, so long as the chain is definitely sufficiently lubricated. Constant, clean, lubrication of roller chains is usually of principal importance for efficient operation in addition to correct tensioning.