What’s the difference between Type 4 and Type 3R enclosures?

Industrial enclosures are used to protect sensitive equipment indoors and outdoors in nonhazardous locations. You may require an industrial enclosure if you are extending your IT network into warehouses and other facilities where environmental conditions must be considered. In this tech tip video, Chatsworth Products (CPI) expert and product marketing

http://www.chatsworth.com/blog/tech-tip-video-converting-a-ul-type-4-industrial-enclosure-into-a-ul-type-3r-for-optimal-drainage/