Dingle cog

The Dingle cog is a two-speed track cog for fixed gear bicycles manufactured by Surly. It was released in early 2007 and seems to be the first ever mass-produced multi-speed fixed-gear cog that is compatible with standard track hubs and lockrings.

Three gear combinations are available:
* 17t and 19t
* 17t and 20t
* 17t and 21t

The Dingle cog is designed to be used with either one or two chainrings. When used with two appropriately sized chainrings, the rear axle's position in the dropouts can remain almost the same and still allow a relatively large difference in gear ratio between the two combinations. With only a single chainring, the rear axle's position will need to change to accommodate the difference in chain wrap between the two gears.