As noted above, the lockring only holds the sprockets to the freewheel body, which as is with all freewheel bodies, threads to the hub.
A number of years ago there was a fellow from Great Britain who made a tool which fits this lockring (but not the Sunrace lockring) but I can't find it listed at the moment.
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Bob
Enjoying the GA coast all year long!
Thanks for visiting my website:
www.freewheelspa.com