Loop and hoop fastener:The extra loop and hoop fastener helps keep the zipper in place and prevents heat from escaping from the top of the zipper as well. Popular choice:Rectangular sleeping bags are a popular choice for car campers. You can bring a rectangular sleeping bag into the campground, and this one is a warm and roomy option for families and car campers. Any position:In an envelope sleeping bag, you can sleep in almost any position you like. A rectangular bag offers more freedom of movement and a variety of sleeping positions. Multifunctional zipper:The envelope sleeping bag has a zipper down two sides, running the length and the width of the bag. You can either unzip your bag for ventilation if you are feeling too warm or completely unzip your sleeping bag and use it as a large blanket. Lightweight & Portable:This super light sleeping bag weighs about 950kg/2.1lbs, and comes with a carrying bag for easy storage and transport. You can hang it on your backpack and carry it with ease. Zipper with double sliders for your convenience.