The BG801HAK P3 is a high altitude conversion kit for BG801 models that are field converted to use propane. It is works with all 45000, 70000, 90000 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 7501-10000 feet above sea level.

This kit includes: 

80W51 (Switch-Pressure .55 WC) high altitude pressure switch 

BG11K45 high altitude propane conversion kit (low pressure switches are included with all Blueridge LP conversion kits for additional piece of mind and to protect your investment)