In the US, these are an accessory wheel, you can include in your build directly on the MBUSA website. Specs are:

$2,130
19-inch 6-spoke alloy wheels

2015-C-CLASS-SEDAN
Add to your car’s poise and performance without compromising its engineering precision. These light-alloy 6-spoke wheels feature a shimmering Titanium Silver/polished finish.

Wheel size: 7.5 J x 19 ET 44
Tire size: 225/40 R19 XL

Option for rear axle:
Wheel size: 8.5J x 19 ET 56.5
Tire size: 245/35 R19