There are actually two types of links alternating in the bush roller chain. The 1st type is internal links, having two internal Transmission Chain plates held with each other by two sleeves or bushings upon which rotate two rollers. Inner links alternate with the second type, the outer links, consisting of two outer plates held collectively by pins moving through the bushings of the inner links. The “bushingless” roller chain is comparable in procedure though not in construction; instead of individual 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. 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 original power transmission chain varieties lacked rollers and bushings, with both the inner and external plates held by pins which straight contacted the sprocket tooth; however this configuration exhibited incredibly rapid wear of both the 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 wear over a larger area; however the the teeth of the sprockets still wore quicker than is appealing, from the sliding friction against the bushings. The addition of rollers surrounding the bushing sleeves of the chain and offered rolling contact with one’s teeth of the sprockets resulting in excellent resistance to put on of both sprockets and chain as well. There is even very low friction, as long as the chain is certainly sufficiently lubricated. Continuous, clean, lubrication of roller chains is of main importance for efficient operation along with correct tensioning.