You get what you pay for.

Bosch invented the aerotwin design and the genuine parts are superior in every aspect- the standard of components and materials used, rubber formulations, aerodynamic control and longevity.

The rerofit range, although not an OEM product, uses the same technology.

Most non Bosch products using the Aerotwin concept are basically copies and in general of inferior quality, so be careful- there are many products advertised as Bosch, but not Bosch.

Best to double check.