This guide is intended to help you decide if you really need one of these bags.
water resistant outer cover ideal for bivi type camping
sleeves for ability to use other camping equipment while still inside the bag
horizontal zip halfway down the bag allows you to slip the legs out and effectively use the sleeping bag as a Parka in bad weather
front zip for easy entry and exit
breathable front panel on the bag reduces condensation inside.
keeping warm inside at night with the arms in the sleeves is difficult, better to turn the sleeves inside out and pull them inside the bag to retain body heat
waterproof outer skin is noisy when moving in the bag against bed rolls etc
lining is quilted with low thermal properties, designed to be used fully dressed rather than stripped down night wear
bulk and weight, compared with other sleeping bags of similar thermal performance the german army bag is heavy and bulky when rolled into its own unlined hood.
a cheap 3 season mummy style bag will probably perform better heat wise, be more compact and lighter in general use. think before buying this type of bag in preference to a normal one