This #10 3-hole silicone stopper is used alongside the BrewBuilt CoolStix for Fermonster Carboys. The holes are for a 1/2" CoolStix, an airlock, and a thermowell. The holes measure 0.500", 0.413", & 0.375"

Compatible with Fermonsters and our Plastic PET Carboys listed below under "You Might Also Need".

Please note: the stopper will fit all sizes of Fermonsters, however we only recommend using the 1/2" CoolStix with the 3 & 6 gallon sizes. This is due to dimensional restrictions and cooling power limitations.