This is an aluminum and stainless enclosure providing redundant power, 4 5.25″ external drives, 2 3.5″ external drives, and 2 internal 3.5″ drives. Both Intel and Sun motherboards can be accommodated. The chassis passed Mil Spec 901D (Barge Test). If you are not familiar with the Barge Test, go here for some entertaining video (Large File – 27Mb).