The Webasto Thermo Top EVO 5 uses 22mm exhaust. For standard vehicle installations please see - https://www.butlertechnik.com/item/Webasto/or-Eberspacher-Exhaust-Pipe-Stainless-Steel-Flexible-22mm-337390-36061100-Meter-Lengths/5JH
If your heater is installed on a Marine application, please check the hull skin fitting installed, this could be 24mm OD. If the hull skin fitting is 24mm OD, you will require a 22-24mm exhaust adapter - https://www.butlertechnik.com/item/Webasto/Air-Top-2000-heater-exhaust-adapter-22mm-to-24mm-92641A-1320382A/5NQ
Then you will be able to install a complete length of 24mm exhaust - https://www.butlertechnik.com/item/Eberspacher/or-Webasto-Exhaust-Pipe-Flexible-24mm-CUT-TO-LENGTH-36061296-90394a-Meter-Lengths/5JJ
For 22mm exhaust please use heavy duty exhaust clamps - https://www.butlertechnik.com/item/Webasto/Clamp-for-22mm-ID-exhaust-flex-1320103A/5ZR
For 24mm exhaust please use heavy duty exhaust clamps - Eberspacher Webasto exhaust clamp 24mm exhaust | 15261102 91383B | Butler Technik
