All nuvi models will support SD cards up to 8GB in size.
Last modified on: 11/18/2012 link:modified 3/26/17 https://support.garmin.com/faq Search/en-US/faq/content/Us L6M...
The Garmin GPSMAP 64, 64s and 64st make up a set of midrange, handheld GPS mapping devices for hikers, geocaching enthusiasts, marine travelers and others who enjoy the outdoors.
The features of the walkie talkie shaped devices in the GPSMAP 64 series vary from the basic GPSMAP 64 model to the more advanced 64s and 64st models.
I transferred all the new files onto my unit & the job was done.
I wait a few seconds and fire up Garmin Express and it continues where it left off at 50 % and within a matter of minutes the entire download is on the SD card.Update: Garmin FAQ 10/16/2012 ----- Garmin ----- Question: What is the slot on the side of the nuvi used for?Answer: The slot on the side of the nuvi is used for a Secure Digital (SD) card. These memory cards come in various sizes and are usually sold as either a micro SD or regular SD cards.Depending on the device that you own, the nuvi may use either one of these SD card sizes.SD cards can be used to store files such as MP3 audio files, JPEG picture files,2 or supplemental mapping.I used Map Updater on both my 255WT using Alandb cloning method and all went extremely well without a hitch.