The "6 X MM club, will consist of anyone able to catch a fish "measured in millimeters, because they're too small to measure with a standard ruler" and caught on 6X or, lighter, tippet!?
Here's my entry, caught on 7X, at about 24mm on the Kilchis River here, in Oregon this summer.

Thankfully, the strain on my rod wasn't enough to damage the blank, but I still, didn't run the risk of stretching my net bag out of shape, so hand landed this killer without using it. That will add about 3 more points to my overall score at least!