Although there are more expensive and heavier bivy's in OR's lineup I wanted something ultralight that would work in Alaska and Montana for all seasons. In winter the bivy extends the Plasma 15 rating closer to 0 degrees. The photos show how I added an upgrade 3rd party mosquito hood which allows the ultimate in protection during summer pursuits. My Marmot plasma 15 with Thermarest insulated NeoAir mattress fit inside surprisingly well. I could add a closed cell foam pad as well and still have room.