This is factory size of heating module for 1994 Audi A6 with ABK engine. If you need to replace it, buy 272 mm height, 150 mm width and 30 mm in depth equipment. Actually, the heaters for motors with model code ADR in A6 can work properly for a long time. A heat exchanger is main part of Audi A6 winter climate equipment. There aren’t usually any problems for 1995 cars with 2.0 motor with microclimate.
It also may be seen in Audi as bad heating, especially in 1996 year of production. Don’t forget original dimensions for Audi A6 1.9 heater - 272 mm height, 150 mm width, 30 mm depth. The visual problem in 2.5 A6 with heating radiator problems is cooling fluid coming out.