3M Sound Damping Foil Tape

I also use a product called Dynamat at home and in car audio, and similar products by other names, ( Blue Tac, U.S.C. ). A very useful butyl based product when used in the right application. Be a little cautious it's not easy to remove completely.

Using these products on the shelving your gear is on should be fine. The main concern would be blocking the air circulation that flows around the components.

Putting products like these inside your gear can cause overheating, shorten its parts life. Worse yet, a safety hazard. All of our audio gear dissipates heat. A lot (possibly all of the heat) of this heat is dissipated through the metal cabinet itself. When you put some of these products inside of your components, can also lead to thermal runaway type of situation. You need to know what your doing.

If you don't have any temperature measuring devices to check the running temp of the unit running continuously before, and after installing these products, it can be even more risky.

Thanks for all of the responses. I started my search for this material with the intent of applying it to the MDF shelves of my DIY rack. I have also heard of some mods to electronics that included applications like this, but this is not my first purpose for seeking this. I will try it on the bottoms of the shelves and see how it goes. Not very expensive stuff, so the risk is low to try it.