Our filter / sparging stones have an internal thread of 5-40. These should be used with low pressure 1/8” or 1/16″ ID polymeric tubing. The threads are actually small barbs that grab onto the tubing, ensuring a secure fit.
NOTE: It may be important to use the internal threaded sparging stones instead of those with fittings to avoid the mixture of many different components in the solvent. This type of connection of the tubing and the stone should not come off in situ as can happen with the tubing/stem configuration.