This field controls the sort order. The default sort order is alphabetically on the title. Other useful sort orders include Cost, LowGear, etc.

1. Cost
    Sorts by cost, with the least expensive bikes first.

2. LowGear
    Sorts the bikes starting with the ones that have the lowest gear. (The lowest cog ratio).

3. RearCogs
    This sorts by the smallest cog on the cassette. It is useful for grouping together all the bikes that have a given cassette, such as 11-36. That tells you that the 11-36 is a standard cassette.

4. BrakeType
    Useful to see how many of the bikes have a given type of brake. Eg: As of today, most are CableDisk.

From the document: Form Help for Bike Lister