The MicroSD Card expands the HMT-1’s internal storage for additional photos, videos, and applications. 64GB capacity provides an extra 8+ hours of video recording at 1080 full HD, 128GB provides an extra 16+ hours, and 256GB provides an extra 32+ hours. The card meets UHS Speed Class 3 (U3) and Video Speed Class 30 (V30) for fast capture and transfer speeds (30MB/s minimum sustained write speed and 90MB/s max read speed), and has a microSDXC form factor.