Hi Tony_1,
There isn't a listing for the maximum read and write speed the VIXIA GX10 can use. That camera is compatible with SD, SDHC, and SDXC memory cards. The UHS Speed Class it is rated for is Speed Class U1 and Speed Class U3, and the SD Speed Class it is rated for are CLASS6 and CLASS10.
If you would like to view that information in the manual it is on page 29. If you need a copy of the manual it is available HERE. Once you are on the web page click on the Manuals tab and the one to reference is named VIXIA GX10 Instruction Manual NTSC.
