This allows me to go out of my preamp 12v trigger (a 2.5 mm jack) to my power amp 12v trigger (a 3.5 mm jack) with a 3.5 mm cable.

Works perfectly. I needed to adapt size and also wanted mono to stereo, so I needed to use 2 pieces to accomplish this. 2 pieces is a little clunky on a handheld radio, but it works great for our purposes. I will buy from Monoprice again...without hesitation.

I'm sure the part is fine, but it does not work with the Bose Quietcomfort 45's. I blame Bose. The the audio becomes mono (left ear only) unless the plug is pulled out of the socket slightly, which is not sustainable as it just falls out without the pressure fit.

good product and good price.
longer than expected delivery time but it's worthy.

A description including dimensions would have been helpful. The plastic surround was too wide to fully insert into my amplifier's 2.5mm female 12v trigger port but I was able to shave a side of the adapter down enough to fit. Otherwise it functions as intended.

These jacks are perfectly fine, I assume, but I ordered the wrong length. So, I couldn't actually use them. Perhaps there's one that matches the jack in this comparison photo?

I have the bose qc35. The adapter is too thick at the base and creates some issues with connection.

I bought the wrong adapter. Make sure you know your sizes and compatibility.

Got the wrong size plug for my TENS unit, figured out the lines on these plugs indicates how many channels they split the signal into, got this mono to mono one and all set.

Used to extend a 2.5mm IR emitter cable