This is a Space65 custom keyboard by Airpotter with the help of Oldcat. This video shows the sound difference with and without mkultra.click plate foam.
The foam goes between the plate and the PCB.
The keycap set is GMK Calm Depths from Kono.store
In my opinion this foam definitely has an impact on the sound. Is it worth it? You decide! What I hear is that the overall sound of the keyboard seems lower-pitched. I think some of the higher frequencies are being attenuated by having the foam there. Personally, I like the effect it has. The foam is relatively inexpensive too, so I can easily recommend this product.
Full disclosure, the plate foam was given to me as a sample in return for doing my best to give a fair review of it.
Apologies for the strange video artifacts around my fingers, but this won’t affect the sound. I guess my video encoder was glitching a bit.