64gb Samsung Pro Endurance microSD. Have thought about upgrading to a larger capacity. However, honestly, in a full year of ownership/use, I have never felt that I missed or lost an important video event because of the smaller storage capacity. I would probably feel differently if I either lived in the city with street parking and/or if my daily routine required me to drive & park in multiple public locations throughout a given day. In the above scenario, the number of sentry mode or other important event recordings would go way up... which means a larger capacity drive would probably be needed. Fortunately, I don’t think my current driving & parking habits require anything larger than a 64gb drive. I’ve always wondered how many days of recording I get with a 64gb drive, before it starts to over-write itself. Not sure if there is an easy way to determine this...