The low-intensity SunTube infrared tube heater line offers three models. The reflectors on Model GQ (global quality) rotate independently and all reflectors are in a fixed overlapped position. The SunTube IV Model has rugged, heavy-duty construction to tackle the toughest heating challenges, says the manufacturer. The Stainless Steel Model resists wet, humid, and corrosive environments, the company says. Features of all the models include a 91.7-percent reflectional efficiency design, reflectors that rotate 0 to 45 degrees, a pre-purge cycle, 100-percent safety shutoff, direct-spark ignition, and system validation lights. All three models are available with 40,000 to 200,000 Btuh inputs and tube lengths from 10 to 70 feet.