The iStar BPU-2535v2 2½" to 3½" drive adapter cage is a versatile product that offers flexible uses. It can function in an external 3½" drive bay for easy hot-swap access capability to dual 2½" SATA drives. Or it can be used as a simple internal drive bay adapter for those looking to install an SSD or two into their desktop. Both door latches are lockable using the provided hex-shaped keys for security. And since the SATA1 data and power ports are located in the standard spot, it will even work in those 3½" bays with hot-plug connectors, although you would lose access to the SATA2 port in that situation.
The only problem I ran into was when mounting the iStar adapter in the Cooler Master internal drive tray bracket. The rubber isolation posts did not line up or fit correctly in the holes, because they're made to fit a 3½" hard drive, and the iStar is keyed like a floppy drive. I made it work by removing the posts and utilizing the screws that iStar provides with the product, which have a smaller and finer thread. Those cases that use snap-on rails or other tool-less post mounting may experience similar issues. Cases that have traditional metal-sided bays with slotted mounting holes for screws could easily accommodate the iStar in either external or internal configuration.
I found the iStar BPU-2535v2 available online in the $30 to $40 range. Although this is slightly more expensive than other 2½" to 3½" drive adapters such as the Icy Dock units, the iStar is constructed of aluminum rather than plastic, and features dual, lockable, hot-swap slots for your 2½" drives. The BPU-2535v2-R version is also available if you need hardware RAID capability built-in.
OCIA.net awards the iStar BPU-2535v2 our Gold Seal of Approval.