Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 59)

Inserting/Removing Cards
Insertion
Removal
This camera accepts two cards. Recording is possible as long as there is at least one
card in the camera.
With two cards inserted, you can select one card to record to, or you can record the same
image to both cards at once (
).
Insertion
1.
Open the cover.
Flip out the card slot cover release handle (1) and turn it as shown by
the arrow to open the cover.
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