I recently got the Oregon 400T and purchased City Navigator NA 2009. I only selected my state and the surrounding 12 states / provinces maps' (From CN NA) to upload to the Oregon (we rarely ever travel out of that range), and still don't have a micro SD. For example, I have Minnesota, North and South Dakota, Nebraska, Kansas, Iowa, Missouri, Wisconsin, Michigan, Indiana, Illinois, Manitoba, and Ontario and am only using about 75% of the Oregon's storage. I do have a small Geocache and Waypoint set (Approx 108 or 10%), keep my tracks small etc.