A heater is only as good as its duct run. This is the full Webasto high-temp ducting catalogue: 60mm and 90mm louvers, tees, flex-duct clamps, inlet grates and the 22mm combustion-air and exhaust parts on the burn side.

Adjustable louvers let you aim heat; adjustable closeable louvers let you shut a run down entirely, which is how you send all the output to the foot of the bed at 2am instead of heating the galley. A tee splits one heater into two outlets - the standard trick for warming both the living space and a wet-boot locker. Duct clamps are cheap and are the number one cause of a rattling install when skipped.

On the combustion side, the stainless exhaust muffler is the difference between a heater you can sleep next to and one you cannot, and the 22mm combustion air elbow keeps the intake pointed away from road spray. Everything is listed by OEM part number. Shop complete kits in Van Air Heaters.