The main purpose of the camera housing is to protect the camera's inside from the elements on the outside. The criteria to keep in mind are as follows: insure proper housing size for camera/lens combined, level of weatherproof/waterproof required, is either a heater and or a blower required. These are the main questions to be asked when trying to determine which housing to use. In special applications one may require :a explosion proof housing, bullet proof housing or that the housing be pressurized with a inert gas such as nitrogen. If your having trouble selecting the right camera housing for you, then please call at (800) 572-3390 and talk to one of our factory trained sales representatives to assist you with your selection.