... is ANSI standard #40, where the 4 indicates the pitch of the chain in eighths of an inch, and metric #8, where the 8 indicates the ... roller widths: 5/32" is used on cargo bikes and trikes, 1/8" with the common low cost coaster ( ... and mountain bikes.The Wikibook, "Bicycle Maintenance and Repair", explains that the difference between derailleur chains commonly labelled 8-speed, 9-speed, and 10-speed is ...