Semi-Rectangular: I call this the cross. This backpacking bag is rectangle-shaped ahead and afterwards slenders along towards the feet. With this type, you obtain added space, but not as much weight as a true rectangular resting bag. For those who are claustrophobic, like me; we can reach sleep a little better inside a bag with added room in it and still have some benefit from the form.
There are some sacrifices though in opting for a bag that supplies all that space to move. The most significant possibly being your home heating capacities and heat scores. See, while having all that space is nice, much like having a big house with tall ceilings it takes a great deal even more to heat the within. The added room requires more effort to keep cozy and also for that reason, isn't really as efficient for shutting out the cold as a mummy bag is. Obviously having said that, the pyjamas you prefer to oversleep can aid make up for the heat differences between the bags also ... approximately particular temperature levels. Suffice to claim that artic temps could call for more than a teddy or set of boxers.
There are primarily two types of sleeping bags. One is the mommy bag and the various other is the "traditional" rectangle-shaped resting bag. Currently mind you, ain't nothing incorrect with old school in any way. It might be your preference once you uncover just what it's like verses the mommy bag.