Park Tool FRW-1 Freewheel Remover Wrench
The FRW-1 is a one-inch socket and securely holds freewheel and lockring tools (FR-1 through FR-8 plus the BBT-5) for removal and installation. Features an investment cast head with locking setscrew and a long, round, vinyl dipped handle for superior leverage.
Always use a skewer or axle nut to hold a cassette/freewheel tool in place during removal.
This is another one of those tools that hits it out of the park. In a really specific way. Adjustable wrenches are a cheaper alternative, but if you're removing cassette lockrings on the regs, then this tool is tough to beat.