Accurate Ring Positioning – Provides the most reliable way to square piston rings in the cylinder bore for precise end-gap measurement, improving overall engine setup consistency., Dual-Diameter Design – Features two machined sizing steps, allowing one tool to service 4.000″ through 4.230″ bore diameters simply by flipping it over., Durable 6061-T6 Aluminum – Made from high-strength anodized aluminum for long service life, smooth operation, and resistance to shop wear., Works with Head Studs Installed – Outer diameter is engineered to clear installed cylinder head studs, eliminating the need to remove hardware during measurement., Open-Center Configuration – Hollow center lets you visually confirm the ring is fully seated and square in the bore, making it more accurate and easier to use th.