HDDs in the 2.5" form factor are getting more and more popular as their storage capacity is growing. It is only consequent to employ them in servers. That's why ICY BOX offers a backplane that fits into a single 5.25" unit and is for four 2.5" SATA HDDs. The height of the HDDs may even be 15 mm, for greatest storage capacity. This ICY BOX works reliably even with huge amounts of data being transferred. That's a great recommendation for the hard duty in RAID systems. Accordingly demanding is the layout of the cooling. While the aluminum casing cools two 40 mm fans work reliably and silently. Everything is as solid and safe as you might know it from the ICY BOX backplanes for the "big ones".