Screw/seal assemblies are used to attach the fuel transmitter to the aircraft's fuel tanks. The seals are a special Viton rubber Stat-O-Seal that do not degrade or swell with avgas and are built into a special stainless steel washer. A slotted screw with safety wire hole and a washer is used for Piper aircraft. Please note that the washer must be between the seal and the screw head.