Gasket (old # 54F or newer # 1030541 ) used for all size Adapter Nuts on Autotrol Adapters used on all versions of the Autotrol By Pass Valves and for direct connects to older 168 Valves and newer 268 Performa Valves.
Normally you should order Two.
One for each Adapter Nut connection.
Note: Adapter Kits already include two of this part.