The POB is a low cost but durable box alternative. The POBs are made out of polypropylene, and comes in two different heights (6 and 12 inches). Since width and depth are the same, the POB 6 and POB 12 are stackable. Dividers are available for the POB 6 for storing smaller non-critical parts and tools which can withstand standard movement of transportation. The POB is a good choice when a higher IP grade is not necessary.