Smoke Composites is a firearm accessories manufacturer located in Minden, Nevada. The company is specialized in making carbon fiber parts for AR-15 rifles. As you can imagine their products have the main advantage of the carbon fiber material – they are extremely lightweight. Lightest version of their buffer tube/stock weighs less than 4 oz (112 grams (3.95 oz)).
The main body of these stocks are made of 35-50 carbon fiber and the threaded portion is made of 7075 aluminum alloy. Smoke Composites offers the stocks in two lengths called Short Pull and Long Pull. The first version is for carbine length buffers and springs and the Long Pull is for the rifle length components. These stocks work with any mil-spec buffers and buffer springs. You can also order a custom length stock, but that will cost you additional $35.
They also have two versions of the butt plate portion. One is called Open Shoulder Plate and the other one is called Closed Shoulder Plate. The latter has an additional strap attaching the toe of the butt plate to the buffer tube.
The longest (rifle length) and heaviest (closed shoulder plate) version of the stock weighs a little less than 5 oz. So the difference between lightest and heaviest versions is only about 1 oz. Here are the tech specs for different types of Smoke Composites stocks: