QPR Piston Rings CLS-500-4 H20 3.8 x 3/8 STD

 for heavy-duty commercial air compressors
Specification Breakdown
  • CLS-500-4: The core model series identifier. The -4 usually designates a 4-cylinder set or a specific 4-piece ring configuration.
  • H20: Internal manufacturer compound, style, or application code (frequently indicating a heavy-duty, high-heat, or specific coating configuration).
  • 3.8: Represents a 3.800-inch cylinder bore diameter.
  • 3/8: Represents the individual ring width/thickness (3/8") or the cumulative thickness stack for the groove.
  • STD: Stands for Standard Size. This means the rings are designed for a factory-spec cylinder bore that has not been bored out or machined oversize (such as +.010 or +.020).
  •  heavy-duty industrial compressor pumps (such as older Quincy, Saylor-Beall, or Kellogg-American air compressors).
Items are from the estate of my brother. 
He was a General Motors master auto mechanic for over 60 years. He worked for several General Motors New Car Dealerships from 1962 to 1988 in Orange County, CA.
He owned his own auto repair shop in Orange, CA. from 1989-1993. And then in Garden City, ID. from 1993 until his death in June 2025 at age 85.

He collected coins, stamps, automobile memorabilia, classic automobiles that he restored, Car Parts for GM Cars, Plastic Model car kits, Diecast Model Cars, Model Trains, Hallmark Ornaments, and other things.
I do my best to describe items as accurate as possible.