Air Compressor Repair Parts Mercedes Benz Trucks with OM352 - OM314 - OM366 Engines. Piston Diameter : 77 mm ( not to be confused with 94 mm , Ebay Item number Kit contains all parts in the Photo We also sell the Air Compressor Bearings, contact us if you need those. Ring Thickness : 2.5 - 2.5 - 3.0 - 4.0 (mm).