This set of three MB mag housing gaskets comes in 3 thicknesses.
0.5mm (standard) 1.00mm and 1.5mm.
The dimensions of all engines will vary, especially with new rebuilds, or with an engine that's been machined after welding.
Crankshafts can vary in width, casings and mag housings can vary, and you never know what gap you will get between the crank and mag housing on assembly.
This gap should be 0.5 - 1mm to be safe.