[Hectic]

Only guns i had issues fitting the modify rubber in was vfc's (all rubbers i find a little big, or the chamber too tight) the nub may be a little narrow (never measured) but that would explain why the promy bridge or flat nub work beter than the modify lol
even out of spec the modify is loads beter than any stock hop, but i still would suggest the prommy, tho the rubbers have been hard to find even in japan and china