I started with flow through for my TST system, but had tons of issues with them. They didn't interface well with the extensions I had on at the time. Replaced with cap style, I'm down to only two of the flow through's left.
I found them slow and difficult to get air through, and a couple times had failures after doing so.
Eventually I trashed the extensions. Should have done that first thing!
The caps are no different than removing a dust cap to air up when needed. I took the security covers off, as have a lot of folks.
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