Astro Essentials Compression Ring problem

[Aramcheck]

I just bought two Astro Essentials Compression Rings for my SW 200dps & SW130dps. Both rings fit the 130dps ok, but neither seems to fit the SW200dps. When I try to screw the Compression Ring into the focus tube it just falls into the tube & appears to have 1-2mm lateral movement.

What am I doing wrong? Holding the old ring next to the Compression Ring, the thread and diameter look to be the same.

Has anybody else had this problem with the Compression Ring & SW dual crayford focuser? Would PTFE tape help?

Many thanks
Ivor

[wulfrun]

Apologies if this is too obvious...doesn't the 200pds have a 2" focuser?