It happens here and there, someone with a coarse threaded connector orders a fine thread or vice versa. There is a very subtle but important difference in threaded filter model numbers to be aware of.
MPT stands for Male Pipe Thread and refers to fine threaded filter connectors.
SAE refers to a coarse threaded filter connection.
When ordering replacement spa or pool filters that have a bottom threaded connector online, pay attention to the model number. If the model number for example says 6CH-940MPT, then it says very clearly that it is a Male Pipe Thread (or fine) connector. Other filter models may have an M appended to the model number to refer to a male pipe threaded connection when there is a similar model/part number without the M that may refer to SAE or coarse threaded connectors.
In any case, be sure to read and re-read the description of the filter you are ordering before clicking on the order button to be sure you get the correct thread type.
One more hitch with threaded filters is that there may be a female end (threaded socket) to the filter or a male end (threaded pipe or protruding thread) to be aware of.
Of course, for those of you without threaded connectors, you don’t have to worry about any of this.
For those with threaded connectors, you may also want to read more about the difference between MPT and SAE connectors.
Order the type M filter which is similar to the 6CH-940MPT and has a male pipe threaded fine connector here.
Order the type filter with coarse thread similar to 6CH-940 here.
Female Threaded Connectors
Note that if the filter does not have a male threaded connector, but a female threaded socket, then the socket size that is listed as a nominal pipe thread size may be, say, 1-1/2″. That would not actually be they physical measurement of the inside diameter. A 1-1/2″ coarse threaded socket actually measures about 1-7/8″ inside diameter (I.D.) for your reference.