The Sony HXR-FMU128 Flash Memory Unit is an optional recording device compatible with Sony's HXR-NX5U, NEX-FS700, and NEX-EA50M camcorders. It allows you to record to two devices simultaneously, (drive and SD card) realizing an instant backup in the desired format.
The device is capable of recording exceptionally long run-times. For use with the HXR-NX5U, it attaches directly to the back of the camera and can record 11 hours of footage without offloading. Used with the NEX-FS700, it slips into a slot in the camera and stores 10 hours of HD at the camcorder's highest quality (28 Mbps). Used with the NEX-EA50M, it permits extended recording times exceeding 12 hours at 24 Mbps and 10 hours at 28 Mbps.