Cassette Lockring or Freewheel Tool with Handle - FR-5.2H - from Park Tool USA

Cassette Lockring or Freewheel Tool (with handle) - FR-5.2H - from Park Tool USA

Also fits Shimano disc brake lockrings

The FR-5.2 has 12 splines that are approximately 23.4mm across

Note: Always use a quick release skewer to hold the tool in place and snug to cogs when loosening

For solid axles, use the axle nut

Note: You will also need a chain whip tool to hold the cog in place.

Weight: 61.6g (2.2oz) 

Park Tool Reference: FR-5.2H