Service BMX bikes for yourself or others? If so, you must have a Park Tool FR-8C 4-Prong BMX Freewheel Remover. This highly specific tool is used to un-thread four-notch freewheels from flip-flop BMX hubs with 30 x 1mm threads. The thin wall construction of the insertion zone allows for use without removal of hub cones and locknuts, which certainly makes your life easier.

The FR-8 design is stout, made from heat-treated alloy tool steel, and it's one inch base can be used with 1" wrench, though most shops choose to mount the interface in a bench vise so the wheel itself can be used as leverage. The FR-8 has four notches approximately 25mm across measured inside to inside, and is quite distinct from the FR-6, which is used for most other BMX and single-speed freewheels.