This #6.5 silicone stopper fits glass carboys or 1.5" tri-clamp ferrules. It has two drilled holes to accomodate racking canes, thermowells, and airlocks. One hole is 3/8" that will fit an airlock and the other hole is 1/4" that will fit a racking cane or thermowell. You may need some lubricant to aid a racking cane or thermowell through the hole.