This Propex 22mm stainless steel marine through-hull fitting was originally designed for marine applications but many have found it useful in land-based installations of their HS2000 or HS2211 heaters.
This fitting provides a passthrough for the heater combustion pipes and dissipates the exhaust heat via a second outer radiating plate.
Note: when used in marine applications, install the fitting with the combustion stubs pointed up and toward the interior of the cabin. Then route your combustion pipes with a gentle bend to your heater.