Piston Rings 4.040 Bore File Fit MAHLE pioneered the use of piston ring simulation and computer development tools to develop rings that provide free horsepower by successfully minimizing friction. The difference is evident on the dyno and on the track. MAHLEs ultra flat ring flanks maximize ring to piston sealing. The top ring is a ductile iron, plasma moly, barrel face configuration. The second ring is a cast iron, reverse twist. The oil rings are a 3-piece style and are offered in both standard and low tension. A large selection of coordinated piston ring sets are available in 1/16 , 1/16 , 3/16 or 1.5mm, 1.5mm, 3.0mm or ultra-low friction .043 , .043 , 3.0mm sizes. 4.040 Bore File Fit Low Tension .043 .043 3.0mm Images used may be generic. Actual product may vary. Please give us a call if you have any questions.