There are actually two types of links alternating in the bush roller chain. The 1st type is inner links, having two inner plates held jointly by two sleeves or bushings where rotate two rollers. Inner links alternate with the next type, the outer links, comprising two outer plates held collectively by pins moving through the bushings of the internal links. The “bushingless” roller 
chain is similar in operation though not in structure; instead of Conveyor Chain individual 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. This has the advantage of removing one part of assembly of the chain.
The roller chain design reduces friction in comparison to simpler designs, leading to higher efficiency and less wear. The original power transmission chain varieties lacked rollers and bushings, with both inner and outer plates kept by pins which directly contacted the sprocket the teeth; nevertheless this configuration exhibited extremely rapid put on 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 keeping the outer plates moving through bushings or sleeves linking the inner plates. This distributed the put on over a greater area; however the tooth of the sprockets still wore more rapidly than is appealing, from the sliding friction against the bushings. The addition of rollers around the bushing sleeves of the chain and supplied 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 suprisingly low friction, provided that the chain can be sufficiently lubricated. Continuous, clean, lubrication of roller chains is certainly of major importance for efficient procedure as well as correct tensioning.