There are two types of links alternating in the bush roller chain. The 1st 
type is internal links, having two inner plates held collectively by two sleeves or bushings where rotate two rollers. Inner links alternate with the second type, the external links, consisting of two outer plates held jointly by pins passing through the bushings of the internal links. The "bushingless" roller chain is similar in procedure though not in structure; instead of individual bushings or sleeves keeping the inner plates collectively, the plate includes a tube stamped involved with it protruding from the hole which serves the same purpose. This has the benefit of removing one step in assembly of the chain.
The roller chain design reduces friction compared to simpler designs, resulting in higher efficiency and less wear. The original power transmission chain types lacked rollers and bushings, with both inner and outer plates held by pins which directly contacted the sprocket the teeth; however this configuration exhibited extremely rapid put on of both sprocket teeth, and the plates where they pivoted on the pins. This problem 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 use over a greater 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 supplied rolling contact with one's teeth of the sprockets leading to excellent resistance to use of both sprockets and chain aswell. There is even suprisingly low friction, as long as the chain is certainly sufficiently lubricated. Continuous, clean, lubrication of roller chains is of primary importance for efficient procedure as well as correct tensioning.