Mahle Rings Performance Steel Napier THM-13 4.005 x .043in .135RW Plain Ring Set

This is a set of Mahle OE steel Napier piston rings, part number THM-13. These rings are designed for a 4.005 inch bore with a .043 inch ring thickness and a .135 inch ring width. They are a plain ring set, meaning they don't have specific coatings or treatments beyond the base material, but are well-built for reliable performance in your engine rebuild.

The Napier hook design on the top ring helps to improve oil control and reduce blow-by, which can lead to better compression and a more efficient burn. This particular set is a popular choice for many engine builds where a solid, dependable piston ring is needed to ensure proper sealing between the piston and cylinder wall. They fit right into standard ring grooves, making installation straightforward for someone familiar with engine assembly.