Betta Premium Digital Aquarium Heaters are constructed using high quality materials. They feature a temperature digital display screen, external controller, and a shatterproof quartz glass tube. Also fitted is a new design, built-in guard to protect and stop certain types of fish such as Plecs and Sucking Loach from resting on them and burning themselves. Available in sizes to suit aquariums from 20 litres to 300 litres.