The interior of the bag is actually a soft, synthetic material. Most sleeping bags have a diamond weave interior, same as the exterior. That kind of material can get cold and takes some time warm up after you crawl inside. The material in this bag stays warm so you don't have the initial shock of the interior being cold. The downside to this material is that it does not allow for much movement when wearing clothes to bed. The slicker material allows you to roll around inside with ease, whereas this material clings to clothes which is uncomfortable.
The hood of the bag is pocketed and fits comfortably on the head. There is a single drawstring to tighten the face of the hood. Last time I was out, I was able to tighten it until the opening was almost completely closed, which is beneficial in cold weather. The bag also has a thick draft tube to keep the warmth in.
This bag has a duel zipper system that can be opened and closed from the inside and outside. A Velcro keeper is also added to hold the zipper shut. As with most bags, it also has loops at the feet to hang the bag up to air out. A nice, final addition is a small gear pocket on the inside of the bag that zips closed. This is a great pocket for a phone or iPod.
The bag also comes with its own compression sack. It has 4 compression straps on the sides to compress it lengthwise and 2 on the open end as well. The bottom end has a handle to assist with pulling the bag out. It compresses small enough to fit in a medium sized day pack and weighs about 4.1 pounds.
This is overall, a great bag. In the negative degree weather, it works great with an additional sleeping bag. I hope this post helps you in your decision on choice of sleeping bag. Please comment any questions or comments.