This is a great rug pad made of 100% natural felt fiber at a great price.  I choose the .375" thickness for my 4'x6' entry rug.  If I was purchasing a larger rug I would buy the thicker .50" Eco felt rug pad. 
One side seems to have a tighter weave so I put that side on the wood floor so the rug doesn't move much. 
A good rug pad extends the life of a rug and makes it thicker and softer to walk on.  I only buy natural fibers.  I don't like rug pads with rubber backing.