This is plastic clip at the end of the wiper arm, usually broke off a tab on it while trying to install some replacement. The wipers are of the newer style.

Part number on the underside : W000050335

For Mercedes Benz A-Class W176 2016-2021
For For Mercedes Benz B-Class W246 2016-2021
For Mercedes Benz C-Class W205 2015 - 2021
For Mercedes Benz E-Class W213 2016-2021
For Mercedes Benz Vito W447 2014-2021
For Mercedes Benz V-Class W447 2014-2021
For Mercedes Benz GLC-Class X253 2016 - 2021
For Mercedes Benz CLA-Class 2016-2021It may fit others, if you have a specific model, please ask and I'll look it up.