The grip is fiberglass wrap, its permanently on there, and the whole stock is coated in fiberglass resin as well. The red thing is the little flip open lever for my scope cover. The cheek rest is fiberglassed too, but has a pad over it.
I got the gun used a long time ago, the body doesn't have a few of the bolts that hold the two haves together. It fattened it up a bit and held it together a lot better, there was a hideous seam before.
Close, but I don't think they use fiberglass. There is a mat or cloth type material you add a resin to, the wrap on my grip and cheekrest is a piece of Tshirt with resin to make it hard. I plan on making a body for the chassis out of real fiberglass cloth, just need to make a mold. Currently, it is only a fiberglass resin coating, it has helped tremendously for keeping paint from chipping or wearing off.
You can even use hockey tape as a material for the resin, simply wrap what you want in the tape, then add the resin.
Cause the stuff they used for my cast they dipped in water, then it heated up some and became hard as rock, seriously I had a friend step on the cast, He weighed about 180lbs and It did not even creak.