The reusable FBS3 smart key is compatible with most Mercedes key programmers on the aftermarket.
2 Ways to exchange frequency:
Method 1:
If you have
VVDI MB Tool, it is easy to change frequency in vvdi mb software (update software to latest version)
Select Other Function-> Set key remote frequency/ Update MB smart key
You can set frequency between 315MHz and 433MHz
Method 2:
If without VVDI MB, you can change FBS3 keylessgo smart key frequency manually by soldering/desoldering the FRE resistor (marked red in picture below)