There are two types of links alternating in the bush roller chain. The 1st type is inner links, having two inner plates held jointly by two sleeves or bushings upon which rotate two rollers. Internal links alternate with the second type, the outer links, consisting of two outer plates held together by pins passing through the bushings of the internal links. The “bushingless” roller chain is similar in operation though not in construction; instead of individual bushings or sleeves keeping the inner plates together, the plate has 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, leading to higher efficiency and less wear. The initial power transmission chain types lacked rollers and bushings, with both the inner and outer plates held by pins which straight contacted the sprocket teeth; however this configuration exhibited incredibly rapid wear of both the sprocket the teeth, and the plates where they pivoted on the pins. This issue was partially solved by the advancement of bushed chains, with the pins keeping the outer plates moving through bushings or sleeves linking the inner plates. This distributed the put on over a larger area; however the teeth of the sprockets still wore more rapidly than is desired, 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 leading to excellent resistance to wear of both sprockets and chain as well. There is even very low friction, provided that the chain is definitely sufficiently lubricated. Constant, clean, lubrication of roller chains is of major importance for efficient procedure in addition to correct tensioning.