FYI i read this today , you may already know about it , ( Cool-tubes are a great product which, for very small grow rooms or rooms running lots of lights, can be the only option for running high-intensity discharge (HID) lighting. However, they do have their downsides. Compared to an 'open' reflector, the curved glass in a cool-tube reduces the amount of available light that reaches the plant. Also, glass will block out the UV light that reaches the plant and it is UV that causes Cannabis to create and release her lovely essential oils. )