The FP55 is a generation of 5.25" to 3.5" drive bay bracket that is capable of accommodating two additional 2.5" hard drives or SSDs in addition to a 3.5" device or drive. The FP55 also has two sets of mounting holes so users can choose to install FP55 with its aluminum bezel exposed or concealed behind an existing case's own drive bay cover. If you are building a system in which additional hard drive space is required and there are free 5.25" drive bays, the FP55 is a great choice.