There are two types of links alternating in the bush roller chain. The initial type is inner links, having two internal plates held with each other by two sleeves or bushings where rotate two rollers. Internal links alternate with the second type, the external links, comprising two outer plates held jointly by pins moving through the bushings of the inner links. The “bushingless” roller chain is similar in procedure though not in construction; instead of individual bushings or sleeves keeping the inner plates together, the plate has a tube stamped into it Transmission Chain 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 the inner and external plates held by pins which straight contacted the sprocket tooth; however this configuration exhibited extremely rapid put on of both the sprocket tooth, and the plates where they pivoted on the pins. This issue was partially solved by the development of bushed chains, with 
the pins holding the outer plates passing through bushings or sleeves connecting the internal plates. This distributed the use over a greater area; however the tooth of the sprockets still wore more rapidly than is desirable, from the sliding friction against the bushings. The addition of rollers encircling the bushing sleeves of the chain and supplied rolling contact with one’s teeth of the sprockets resulting in excellent resistance to wear of both sprockets and chain as well. There is even very low friction, as long as the chain is certainly sufficiently lubricated. Constant, clean, lubrication of roller chains is of main importance for efficient procedure in addition to correct tensioning.