The big brother of the 1SKB-iSF2U! This case features a virtually indestructible, waterproof injection molded shell that is lighter, stronger, and more affordable than the previous 4U Studio Flyer, and includes innovative molded-in front and rear rack rails that provide even more security and durability for sensitive studio equipment during travel. As a larger Studio Flyer option, The 1SKB-iSF4U offers a 4U rack mount measuring 15" from front rail to rear rail which safely accommodates deeper equipment, such as the Universal Audio Apollo audio interface. It also provides a 21" x 15.5" adjustable work surface with ample room for laptops or monitors, and a specially molded exterior pattern that stacks securely with all SKB Roto Racks for maximum transport convenience.