The Memory Stick / Floppy Disk Adaptor (MSAC-FD2M) was introduced by Sony in 2000 for use in several of its Mavica line of digital cameras, and allowed the cameras to use a Memory Stick as an alternative form of storage.
The adaptor had the same form-factor as a 3.5-inch High-Density floppy disk, and incorporated a slot for a Memory Stick. The adaptor could be used in PCs (it could also be used in Macs, but was read-only) after installing suitable drivers. The adaptor required two lithium batteries to operate.
In the new Mavica cameras, users had a choice of using floppy disks for storage (as a number of previous Mavica models offered), or a Memory Stick with the adaptor which had the advantage of higher capacity (at the time, this was up to 64 MB).
By 2001, Sony had introduced Mavica cameras with dedicated Memory Stick slots, so an adaptor was no longer required.