Converting a Mountain Bike to a Single Speed Bike. : 6 Steps - Instructables
Double Six Single Speed Converter - Gusset Components
Single Speed Conversion Kit – Origin8.bike
Amazon.co.jp: Bicycle Bike Single Speed Fixie Cassette Cog 17T/18T/19T/20T/21T/22T/23T Fixed Gear Conversion Kit Compatible with Shimano 10/11 Speed HG Freehub Mountain Bike Road Bike 17-32T Freehub Hub Hub Refit Parts All 8