The Defence 4 from Carinthia is a 3-season bag insulated with G-LOFT and should keep you comfortable down to -15 C but can be used in conjunction with other Carinthia bags.
It’s offered in Medium and Long lenghts and features a center zip with draft tube.
www.carinthia.eu/en/defence-4-woodland-p3323
T-Comf (-8c here) is where you can expect a nights sleep. Although tested while wearing a wool base layer. T-Limit (-15c) is the divider between safe and risk. T-Extreme is strictly irresponsible and dangerous; just like marketing the Limit as a comfort area.
Having spent a bunch of nights in D4s and D1+D4, I wouldn’t use the D4 stand-alone for anything outside of summer and warm spring/fall. Unless it’s issued, there isn’t much reason to look at these.