Having exact sizes is usually incorrect, the trigger has to be slightly larger than the colmesh. We assume the marble comes with usual speed to bump off this colmesh and it won't just get near it and go back or something. That is because if trigger and colmesh are same size (or trigger is v. slightly larger), it will not register when the trigger is triggered. Having it larger means it can trigger unless the marble goes in way too high speeds.
(And if that's to do multiplayer, then that's the least of his problems.)
"matan, now i get what you meant a few years back when you said that "the level in mbg is beyond me" after the last rampage i noticed things were insane, and now i truly feel that too" - Dushine, 2015.