Molly Brown wrote:
The dimensions of the O ring for the Mixet shower cartridge is 0.110”
x x 0.565” 0.785”. These measurements correspond to 2.794mm. x
14.351mm. x 19.939mm. The measurements are NOT 3/32” x 9/16”x ¾”.
Anyone that can provide the name of the manufacturer who makes the
Mixet o ring would be greatly appreciated.

Stuff like that is universally OEM-supplied, not available as 3rd party
parts.

"Mixet" doesn't mean anything to me as a name; virtually all
cartridge-type fixtures these days have lifetime replacement/repair
policies.

Best can suggest is either take it to an industrial gasket supply to see
if can match it or contact faucet vendor.

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