The NEMO Jazz Double is a synthetic-insulation sleeping bag built for two, weighing 4045 g total — heavy to carry, but that weight covers two people's worth of insulation and comfort features in one bag rather than two separate ones. A removable bed-sheet liner sits against the insulated, quilted top layer, giving the option to wash the liner without dealing with the whole bag, and an integrated sleeping pad sleeve keeps two pads (or one double pad) from sliding apart during the night.
The tapered shape and draft collar hold in warmth better than a simple rectangular double bag would, and side zips let the Jazz Double be joined to a compatible single bag rather than being locked into a fixed double-only configuration. Given the weight, this is a car-camping or base-camp bag rather than something for a backpacking trip — couples who don't want to zip two separate mummy bags together and who are driving or paddling in rather than carrying gear on their backs will get the most out of it.