The Hydor Theo Heater line features PTC patented thermal technology which makes it among the safest aquarium heater lines on the market. The first shatter-proof heater thanks to the peculiar glass tube. Maximum security: Theo is shock resistant thanks to the PTC heating element and the shatterproof glass tube. Free positioning in aquarium with supplied suction cups. Self-limiting: the patented PTC heating system guarantees operation in complete safety because in case of dry running there is no danger for damage. Two year manufacturer`s warranty.