iStar Hot-Swap RAID Cage @ DragonSteelMods
Quote: "iStar has sent me over the BPU-124V2-SS which allows you to put four 2.5” drives into the space of one 5.25” PC bay. The setup can be used for raid, or you can just use it as a hot swap rack to quickly and easily switch drives and transfer data to and from places. The cage itself is very nicely made, each bay locks individually and there's even two 40mm cooling fans built right in to keep things nice and cool."
Read the review here