There are actually two types of links alternating in the bush roller chain. The 1st type is internal links, having two internal Auto Chain plates held collectively by two sleeves or bushings where rotate two rollers. Internal links alternate with the next type, the external links, consisting of two outer plates held jointly 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 keeping 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, resulting in higher efficiency and less wear. The initial power transmission chain varieties lacked rollers and bushings, with both inner and external plates kept 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 development 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 the teeth 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 the teeth of the sprockets resulting in excellent resistance to put on of both sprockets and chain as well. There is even very low friction, provided that the chain is certainly sufficiently lubricated. Constant, clean, lubrication of roller chains is of major importance for efficient procedure along with correct tensioning.