MAHLE S41905.020 Premium Chrome Piston Ring Set Cummins 4BT 3.9L / 6BT 5.9L +.020 Oversize

The MAHLE S41905.020 is a premium chrome piston ring set engineered for the Cummins B-Series diesel engine family, covering both the 4BT 3.9L (4-cylinder) and 6BT 5.9L (6-cylinder) applications. This is a +0.020" (0.50mm) oversize set, designed for engines with a bored cylinder measuring 4.036 inches, and is compatible with a 17.3:1 compression ratio configuration. Sold as a single-cylinder set.

Key Features:

• Premium chrome-faced top compression ring for exceptional wear resistance and long service life under heavy diesel loads
• +0.020" oversize bore (4.036") for use in freshly bored or worn and oversized cylinders
• Ring materials, coatings, and tension optimized for reduced friction and extended service life
• Compression rings feature a barrel-faced contact area for efficient sealing and reduced blow-by
• Intermediate ring uses a reverse twist design for superior groove-side sealing
• 3-piece oil control ring with stainless steel expander between two chrome-faced steel rails for excellent bore conformability
• Pre-lapped at the factory to seat immediately, virtually eliminating break-in time
• Engineered to be installer-friendly — rings cannot be installed incorrectly
• Manufactured to OE specifications under strict MAHLE quality controls

MAHLE is a globally recognized OEM and aftermarket supplier trusted by diesel engine builders for consistent fit and performance. The S41905.020 ring set is an essential component for any Cummins B-Series engine rebuild or re-ring project involving a +0.020" overbore.