Mercury Piston rings.  22-44-66ci motors.  2.565 bore, 2 9/16".  P/N 39-27841.  Merc 200, 25SS, Merc 500-400-450, MK58, MK55A only, NK78.  For 3 ring type pistons.  Not for the late Merc 2 ring pistons using keystone cut rings. Used rings, who would put used rings in a motor? Truth is more people would than you think. If you are just putting around on the lake they work just fine. Trick is the face of the ring that makes contact with the cyl wall must be without rust & scratches. With a little elbow grease and a scotch brite pad these rings are good to use. 63 Available