This piston rings set includes part numbers 079107065DC, 079107066DC, 077198151L, and 079107065AD, designed for 4.2L V8 engines used in select S5, A6, A8, and Q7 vehicles with CAUA, BVJ, or CGNA engine codes.The set serves as a replacement for the listed OEM part numbers and is intended for standard engine rebuilds.Each ring is manufactured to match specifications, with a cylinder bore diameter of Φ84.50mm (STD), piston diameter of Φ84.490mm, piston pin wrist size of Φ20mm, and pin length of 48mm.Ring thicknesses are 1.2mm (first ring), 1.5mm (second ring), and 2.0mm (third ring).The rings are designed to support consistent compression, promote engine efficiency, and exhibit low volatility with ≤105℃ matter emissions to help minimize deposits and wear during normal.