There are actually two types of links alternating in the bush roller chain. The first type is inner links, having two internal plates held collectively by two sleeves or bushings where rotate two rollers. Inner links alternate with the next type, the external links, comprising two outer plates held together 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 with each other, the plate includes a tube stamped involved with 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 initial power transmission chain varieties lacked rollers and bushings, with both the inner and external plates held by pins which directly contacted the sprocket teeth; nevertheless this configuration exhibited incredibly rapid put on of both sprocket teeth, and the plates where they pivoted on the pins. This issue was partially solved by the development of bushed chains, with the pins keeping the outer plates passing through bushings or sleeves connecting the inner plates. This distributed the put on over a greater area; however the tooth of the sprockets still wore quicker than is desirable, 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 resulting in excellent resistance to use of both sprockets and chain as well. There is even suprisingly low friction, as long as the chain is usually sufficiently lubricated. Constant, clean, lubrication of roller chains can be of major importance for efficient operation as well as correct tensioning.