I needed a 7mm to 9mm adapter for my 2.5 inch hard drive. The bay is the regular size 2.5 inch hard drive and the 7mm drives sit just below the tab that pushes on the hard drive in order to pull it out. This adapter gives my 7mm drives that extra space above so that it can easily be ejected without any problem. This is s 2mm thick adapter. Just use whatever double sided tape you like. I like to use the gray or black foam type. That seems to hold much better.