Incorrect description as the 1" thread on the filter housing is a machine thread, not NPT. So you can connect to 3 NPT male threads /4" thread ends only. But that's fine as you have the connector on either side and you can easily remove/replace the whole thing if needed. There are female threads in the machine thread ends as well as 3/4" NPT, but if you've used them, you'd have no connections. I've installed them before, albeit more expensive brands.
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