Vortex Sound Research

hi all,

looking to buy some knurlies, but i'm unsure on the size diff between M3 or M2.5. is this referring to the length or width of the screw? will one fit and one won't fit my rack?

i've received knurlies with second hand modules, and they have all fitted so far. i've noticed some a bit taller than others. is this what the size is referring to?

thanks

oh, it seems there's a colour difference;

https://shop.befaco.org/175-knurlies

so all mine so far seem to be M3, the darker ones. i guess that's the answer then!