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. Internal links alternate with the second type, the outer links, consisting of two external plates held collectively by pins moving through the bushings of the internal links. The “bushingless” roller chain is comparable in procedure though not in structure; instead of separate bushings or sleeves holding the inner plates collectively, the plate has a tube stamped into it protruding from the hole which serves the same purpose. It has the advantage of removing one step in assembly of the chain.
The roller chain design reduces friction in comparison to simpler designs, Stainless Steel Chain resulting in 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 straight contacted the sprocket tooth; nevertheless this configuration exhibited incredibly rapid wear 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 moving through bushings or sleeves linking the inner plates. This distributed the wear 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 surrounding the bushing sleeves of the chain and supplied rolling contact with the 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 is sufficiently lubricated. Constant, clean, lubrication of roller chains is of major importance for efficient procedure in addition to correct tensioning.
