Wood fired hot tub heater model: - The one internal model that is everything you need. You may choose from three sizes according to your tub. Internal heaters lose virtually no heat, as they are submerged in the hot tub water, but they have nice accessories like heater protection with a mini bar. Your can select AISI 316 or 430 stainless steel option for chlorine and salts treatment.The weight of stoves with chimney and protection, with additional accessories from 30 kg to 50 kg produced stainless steel AISI 430 2-3mm