Has anyone used the Tap Rack Dry Fire Safety Training Aid 9MM/.40 Cal?

TRT loads into an empty pistol magazine. Perfect for use during dry fire training. Keeps the magazine follower positioned so that it will not engage the slide stop of the pistol.
Designed such that the slide of the pistol can pass over the TRT without stripping it from the magazine.

Tap Rack Training Aid Review

Have not used that. I quickly skimmed the video, but I don't see a need for it. I just load a few snap caps in my mags when practicing. It lets me practice tap-rack-assess drills, reloading, etc. It's also helpful because you're actually ejecting the snap cap in the chamber and chambering the next round in the mag, so if you're not racking the slide vigorously enough or you've got your hand positioned incorrectly, covering the ejection port, or some other issue pops up, you'll get feedback.

Just my opinion.

If you don't want the slide to lock back, remove the follower and spring on a couple of mags. Cost=free. Thank me later.

I also like feedback from round being ejected as I tap, roll, rack and roll the gun in the direction of the ejection port.

I got mine for free so I can't address the cost to benefit ratio, but I find them useful for practicing emergency reloads or any drill (one handed reloads for example) that requires that you be able to release a locked back slide by wracking the slide rather than using the slide release.

Yeah, I agree. The only handguns I'd like to have a mag inserted are my subs that use a pinky extension. I prefer to use snapcaps to ensure I see the "round" eject.

Sounds more like a solution searching for a problem.

I like using them with a laser cartridge. As far as taking the spring and follower out, sure but then there’s nothing holding on the base plate on my M&Ps.