I have an inherited 1997 Fuji Odessa MTB. I'm trying to replace the rear cogs (7-speed) and went to remove the (what I believe to be a cassette) then noticed there's no lock ring. Strange, even though the visible ring says LOCK. It says Sun Race on it. I have the Park FR-5 which only fits on the way inner splines that dosnt rotate. Here's what it looks like



Am I missing something or is there really no lock ring on there? How do I get this cassette off? Or is it a freewheel? Help Appreciated. Thanks.

This might help:
https://www.parktool.com/repair/readhowto.asp?id=48

hey i am actually following that guide but i'm still confused because it says "lock" but doesn't have a lock ring so I suspect its a freewheel but would like verification. thanks.

On some 7 speed cassettes the small cog is the lock ring.

You will need 2 chain whips, one to hold the cassette, and one to rotate the small cog counter-clockwise.

Things will look familiar once the small cog is removed.

EDIT: The UG cassette is hard to find, so if you are thinking of replacing, you have only a few choices.

Well I figured it out. It was actually a Freewheel. I managed to unscrew it using the FR-5 lockring removal tool. All is well. Fooled me. Thanks though.

I was going to say that it IS a freewheel. In your picture you can see down along the axle much too far for it to be a freehub setup.