Roller Chains are a series of alternately assembled roller links and pin links in which the pins articulate inside the bushings and the rollers are free to turn on the bushings. Pins and bushings are press fit in their respective link plates. Roller chain may be single-strand having one row of roller links, or mutliple-strand havings more than one roll of roller links, in which the center plates are located between the strands of roller links.
ANSI/ASME B29.1-2011 history
2011ANSI/ASME B29.1-2011 Precision Power Transmission Roller Chains, Attachment and Sprockets