D-400S3 is an ultra compact industrial rackmount chassis with 13.7" in depth. The full size I/O supports all ATX motherboard and up to seven full-height add-on cards. Two external 3.5" drive bays are ideal for iStarUSA 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. One 120mm and 80mm cooling fans in the front and additional one 80mm fans can be mounted in the rear to provide the best ventilation to prevent critical equipment from heat damage. D-400S3 provides server or cluster maximum reliability and performance.