There are two types of links alternating in the bush roller chain. The 1st type is internal links, having two internal plates held jointly by two sleeves or bushings where rotate two rollers. Internal links alternate with the next type, the external links, comprising 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 with each other, 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 original power transmission chain types lacked rollers and bushings, with both inner and external plates held by pins which straight contacted the sprocket tooth; nevertheless this Leaf Chain configuration exhibited incredibly rapid put on of both 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 keeping the outer plates moving through bushings or sleeves linking the inner plates. This distributed the wear over a larger area; however the the teeth of the sprockets still wore more rapidly than is appealing, 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 put on of both sprockets and chain as well. There is even suprisingly low friction, provided that the chain can be sufficiently lubricated. Continuous, clean, lubrication of roller chains can be of principal importance for efficient operation along with correct tensioning