I bought 2.5 yards of this a couple of weeks ago at Hancock Fabrics. It is 46" wide. I weighed it, and it calculates out to 4.6 ounces per square yard (not linear yard). I figure it will weigh about 12 ounces for a 76" long piece to go under my bridge hammock.
Pellon calls it 975 Insul-Fleece. They give very little in specs. They do list this as 45" wide. Mylar and polyester.