With the OEG 4flex® heat pipe, high-quality low-iron soda lime glass is exclusively used. These tubes have been manufactured in Europe with a 30-year experience. That is the reason why we are able to give you a 20-year warranty on the vacuum of the tubes.
With other solar tubes in the market, borosilicate glass is used. This might draw helium in case of high temperatures and thus impair the vacuum. Very often, you will also find visible lines from glass processing with air pockets which might lead to a higher fragility.
