Hi there.
My kit has three Remo Roto Toms instead of the classic two regular tom toms plus floor tom. The roto toms don't have the damping effect of a bottom head or an air column, plus i tune 'em relatively low.
So, i have been using similar gel-based damping pads for a looooong long time. They work very well for killing overtones and general drumhead 'by-noises'.
But, on account of their flexible and adhesive properties they droop, they collect dust and dirt, and they just deteriorate rather quickly, especially at higher temperatures. In short, they're generally messy.
So these promised to solve that, because they are only adhesive on the surface connected to the drumhead, are not droopy and they are washable!
Have had 'em for a while now. My impression is that the basic drawbacks of Gel Damping Pads as described above cannot be COMPLETELY solved. BUT, these are definitely a giant step forward compared to any Gel Pads i've ever had before.
For anyone who uses Damping Pads i would definitely recommend these pads as a big improvement. (Developed by Thomann i think? Isn't Millenium their proprietary brand? So cudo's for Thomann!)