The Dingle (an acronym of dual and single) works great in hilly terrain both on or off-road. They're made from machined, heat-treated CroMoly steel, so they are tough and durable.
They’re available in 3/32" tooth width 17/19T, 17/20T or 17/21T combinations. Recommended for use with 9-speed chains only. You can thread it onto any standard ISO threaded (1.375x24tpi) fixed gear hub and it takes up the same 7.4mm threads as a standard fixie cog. Use a wider lockring to allow you to get a lockring tool onto it. The Andel lockring is a great choice for most standard tarck hubs.
