Straight Ball Valves – Flare or Compression. 90 Degree On/Off Tee Operating Head – Minneapolis Pattern Body. A.Y. McDonald Ball Curb Stops maintain a low turning torque and bubble-tight 300 PSIG water pressure rating due to the PTFE coated brass ball that is supported by two blow-out proof EPDM seals. The end piece joint is sealed with an EPDM O-ring and thread locker. McDonald Ball Curb Stops offer positive shut-off from either direction and are available with a wide variety of end connections.