That be brilliant mate if you can let me know and I'll get a set ordered2.25" sounds about right just going off looking at a ruler. I've got c spanners for my spax coilies at home though so can check properly when I get in from work tonight.
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That's the size of the c spanners I've got mate. Equates to almost bang on 3". No matter what way I measure it I can't get it to either 1.9" or 2.25" lol. Had a bit of a look online though and it seems like the two sizes you found relate to the inside diameter of the lock rings!