|Yeah the larger one is likely just an adapter.|
I assume the smaller disk is a micro SD card, usually used in camera phones. Most card readers only accept the full size SD cards so when you want to look at or transfer those contents using a card reader you need to first slide the micro SD card into an adapter.
I've never heard of anyone using a micro SD card in an adapter in a camera but I guess there's no reason why you couldn't. Normally you'd just buy the full size SD card for use in a camera.
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