Run flat tyres can only be fitted to alloy wheels that are designed to accept them, so unless your C-Class was originally specified with run flat tyres it is unlikely the wheels will be able to be fitted. Later generations of Mercedes-Benz C-Class were available with run flat tyres as an option, so you would need to change the wheels to the correct type before fitting run flats.

We would also recommended fitting four run flats at the same time, as mixing regular tyres with run flats could cause unpredictable handling characteristics.