The iStarUSA D-400S3 4U Ultra-Compact Rackmount Chassis comes with a black bezel and supports all ATX motherboard and up to seven full-height add-on cards. Two external 3.5" drive bays are ideal for BPU-2535 to support up to 4 x 2.5" hard drives. Besides, there is one 5.25" slim drive bay for slim optical device. The 120mm and 80mm cooling fans in the front and an additional 80mm fan (sold separately) can be mounted in the rear to provide optimum ventilation, preventing critical equipment from damage due to heat. The D-400S3 chassis provides server or cluster with maximum reliability and performance.