Do a search in the DIY section for "DIY cool tube" . There are several post on how to make an air cooled reflector using a pyrex bake-a-round which is a glass tube used for baking bread. And all glass used in HID reflectors needs to be tempered for safety reason. You don't want plain glass getting super heated from the HID bulb and shatter while your working on your plants....ouchcan any throw some ideas on making an aircooled hood and does the glass have to be tempered for a 400w hps thanks in advance all!