Free to Fixed: What is a Flip-Flop Hub and Why do you want one? - YouTube
I want to swap my bike from fixed-gear to single-speed, but I don't think my rear wheel has a flip-flop hub. What do I need to buy to achieve this? : r/bikewrench
FIXIE Bike Wheels 27 x 1 Flip Flop Hub - How To Install Freewheel Cog - YouTube