Got a rear wheel from a geared bike collecting dust in your garage? Maybe it’s time you gave it some new life as a singlespeed wheel. Surly's singlespeed spacer kit allows you to use singlespeed cassette cogs on any Shimano-style freehub body.
Surly Single Speed Spacer Kits.
Set of five spacers for converting to singlespeed on Shimano freehub bodies