Based on Interpet's exclusive knowledge of aquarium heater production these heaters are extreme reliable due to their extra thickened safety glass and a plastic end cap for added safety. They ensure peace of mind and good value for money with a 2-year guarantee. They have a positive click-control for precise temperature adjustment. Ideal for aquarium with the capacity of 90-180 litres (20-40 gallons) and length of 91cm (36 inches).