1. Piston Ring-A movable seal used to seal a piston in a cylinder.

2. Compression Ring-Piston ring whose primary function is to seal compression pressures.

3. Oil Control Ring-Piston ring whose primary function is to control cylinder lubrication.

4. Cast Iron Ring-Piston ring composed entirely of cast iron.

5. Chrome Ring-Cast iron or steel ring which has been chromium plated.

6. Molybdenum (Moly) Ring-Cast iron ring which uses a Molybdenum alloy as a face material.

7. Diameter-The outside diameter of a piston ring when compressed to actual bore size.

8. Inside Diameter-The inside diameter of a piston ring when compressed to actual bore size.

9. Radial Wall Thickness-The material thickness between the inside and outside diameters of the ring.

10. Ring Face-That portion of the ring which contacts the cylinder wall.

11. Ring Sides-The top and bottom surfaces of the piston ring.

12. Ring Width-The width of the area across the face of the ring.

13. Free Gap-The end clearance when the ring is in its free state.

14. Compressed Gap-The end clearance when the ring is compressed to bore diameter.

15. Side Clearance-The clearance between the piston ring and groove with the ring in its free state.

16. Torsional Twist-Built in unbalance in the ring which causes the ring to twist in the groove when compressed. This is done to seal the groove as well as the ring face and cylinder.

17. Back Clearance-Area between the inside diameter of the ring and the bottom of the ring groove in the piston with ring compressed to bore size.

(P6)