This is just a dense foam wrapped in cloth. The cloth is attractive and can be removed if necessary. The whole thing is very light, easy to hang etc. As it basically kills all sound starting around 250Hz and above so it should not be used extensively as it will quickly deaden the room - without touching the low end.
On my recent measurements (stereo listening room) I detected a few nasty spikes on the ETC (around -10dB compared to the direct signal) so I ordered a HOFA absorber to see if I can remove them by putting one of these exactly into the problematic spot. Well it works, this is indeed a spike killer product.
I do not agree that this product is overpriced. I have some cheap "acoustic foam" from China (just for testing purposes, they are all crap...) and Basotect foam is nothing alike. Just make sure you know what you want to do with it and don't cover large surfaces / forget treating the low end.
Actually I think my time spent on finding the problematic reflection points costed more to me than this product.