Review on Eco-Plush 7'x11' Rug Pad - Ultra-Thick 100% Felt - Enhanced Cushioning - Available in Various Thicknesses and Custom Sizes by Dale Hing

Seems to be doing the trick. We purchased several of these to protect our natural hard wood floors we just had installed. Other types of matts that do not breathe and/or which have abrasive materails can ruin a floor over time. These arrived promptly, well-protected from the elements and were fairly easy to cut down to the appropriate size with a sharp pair of scissors. Lays flat the first time when setting the rug on top but it will "stick" to the underside of your rug a little bit so to get it perfectly placed and centered under the rug you'll need two people for even small rooms. For big rooms I'd say at least 4.