I have many of these and would not be without them they are most useful on older computers that will not boot via usb or for systems like windows that prefers to boot from an internal drive, I can experiment till my hearts content with new software or different operating systems also backups all in the knowledge that my main most important drive can just be popped in. At one time these were in every recording studio, the artist would just slot this in and have all their work,samples,effects and sequencers available,if you have a few it is like owning several computers without the cost, finally the security aspect, they lock in place and you can't get a more secure computer than one that has had it's hard drive removed!!!