The BG921HAK P1 is a high altitude conversion kit for BG921(Multi-Speed Blower) models that are field converted to use propane. It works with all 45000, 70000, 90000, and 110000 input btu models of that series. It includes all needed parts for the following application.

It is designed for high altitude, propane (LP) applications ranging from 4501-7500 ft feet above sea level.

This kit includes: 

11U65 (replaces11J09) (Pressure Switch Kit-0.60") high altitude pressure switch 

BG11K50 propane conversion kit (low pressure switches are included with all Blueridge LP conversion kits for additional piece of mind and to protect your investment)