1. The 4- hard drive cage occupies 3- optical drive , and it can install 4 x 3.5-inch hard drives. 2. 3.5-inch optical drive hard drive expansion rack hard drive cage,for optical drive expansion. 3. for: DIY optical drive bit conversion hard drive. PC chassis, brand chassis, server chassis, expansion hard drive is a good choice. 4. The product ventilation system is good. Made of high- material, durable, and sturdy for us to use. 5. Standard 4 pairs of hard drive plastic guide rails, hard drives can be assembled without tools. Note: 1. If you to drag the optical drive in a case with 3 optical drive positions, you need to flatten the small iron plate installing it. 2. Please pay attention to the size of the cage and make there is enough room for it in your PC case. 3. HDD Hard Drive Cage only, other accessories demo in the is not included! 4. Some PC Chassis design may not support this Hard Drive Rack. size:16.6cm x 12.8cm x 14.6cm Material:metal colour:Black+silver gray Package Contents: 1 x hard drive cage 1 set x screws 4 pair x Hard drive rail Only the above package content, other are not included. Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.