A6VM80/63 Piston Ring Set (14 Per Set).  Suits the Rexroth and equivalent A6VM series. Appears on Page 6 (item 5) in the Tidal Fluid Power Piston pumps and motor parts catalogue.

Note that this is for the Rings only, not the pistons.  There are 2 rings per Piston.  14 rings per set. Also suits the A7V080 Series.