For the TomTom One XL GPS, you can use any SD card that is 512MB or 1 GB in size. It doesn't support SD cards with larger storage, e.g. 2 GB, 4GB, etc. You can buy these SD cards at many stores that sell memory cards, e.g. for digital cameras, etc. If you can find/buy an SD card categorize as Class 10, it is faster than one that is Class 4. You wouldn't want to go below Class 4 unless you can tolerate slower performance/speed on the GPS device.
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For the TomTom One XL GPS, you can use any SD card that is 512MB or 1 GB in size. It doesn't support SD cards with larger storage, e.g. 2 GB, 4GB, etc.
You can buy these SD cards at many stores that sell memory cards, e.g. for digital cameras, etc. If you can find/buy an SD card categorize as Class 10, it is faster than one that is Class 4. You wouldn't want to go below Class 4 unless you can tolerate slower performance/speed on the GPS device.