Ard, I don't think it's Grey Fox. Grey Fox usually has a fine, dense gray underfur right at the hide, and the guard hairs are usually the barred salt & pepper, light & dark. Even the belly hair on a Grey has the darker underfur. Since the piece posted lacks any dark underfur I don't think it's Fox. Even Red & Kit Fox often have a darker underfur. Of course, there can be a great deal of variance from one animal to another & even from various parts of the same hide.
Here's some Badger. This is from the belly & sides. I believe the material piece that calftail posted is Badger, & likely from the sides rather than from the back.
This a Grey Fox. Looks like from the back of a hide.
The fur piece on the upper left is Muskrat, below that is Beaver & the other piece is also Badger, probably from the back.
This piece is Red Fox, most likely from the back.
This piece is Red Fox, but from the underbelly, and is stained from urine. This is highly regarded for use as dubbing on the Hendrickson dry fly, since the urine stains the fur a nice pink color. Both the Grey & Red can have patches of fur like this, but they don't usually contain the dark guard hairs.