The BG801HAK P1 is a high altitude conversion kit for BG801 models that are field converted to use propane. It is works with all 45000, 70000, and 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 4501-7500 feet above sea level.

This kit includes: 

80W52 (Switch-Pressure .60 WC) high altitude pressure switch 

BG11K50 propane conversion kit (low pressure switches are included with all Blueridge LP conversion kits)