Mine weighs 2 lbs, 5 oz. Good for keeping you dry. But zero insulating ability. There was another thread here maybe 8 months ago discussing bivys versus light weight sleeping bags. The discussion was that a light weight bag at approx half the weight of a military bivy would shed the majority of water, and provide significant insulation.
Two years ago, my bivy was great for keeping the bottom half of me dry under the drip line of a fir tree while snow was melting off. This past year I did not strip down fast enough while hiking in. Got sweated up. About 3 hours later would have given half my gear for a decent bag with some insulation to warm up. The bivy broke the wind. But still froze my butt off. Mine also tends to be noisy when cold.
I am still learning....
