Those who own the MDX-5D Mark lll:
If your housing’s serial number is between 12080001 and 12080198, the rubber part for the ISO button inside the housing must be replaced to use the CANON EOS 5Ds or 5DsR cameras. Please contact an official SEA&SEA dealer near you.
* MDX-5D Mark lll housings with serial numbers outside this range can accommodate the CANON EOS 5Ds or 5DsR cameras as they are.

Those who own the MDX-5D Mark lll ver.2:
If your housing’s serial number is between 143100001 and 143100125, modification at a SEA&SEA official service centre will be required to use the CANON EOS 5Ds or 5DsR cameras in the housing. If you wish to have the housing modified to accommodate a CANON EOS 5Ds or 5DsR camera, please contact an official SEA&SEA dealer near you.
* Modification available as of late July 2015.
* Completing the modification will make the housing more effective.
* MDX-5D Mark lll ver.2 housings with serial numbers outside this range can accommodate CANON EOS 5Ds or 5DsR cameras as they are.

Compatible Optical YS Converters
The Optical YS Converter/C2 for MDX housings is compatible.
The Optical YS Converter/C1 for MDX housings can be made compatible by updating with the C2 firmware.