1Heavy Duty Sender: All fuel sending units are made of selected reed switches and fixed resistors. Sae 5?hole installation mode, heavy 316 stainless steel, strong structure. Signal output is 240 ohms ? 33 ohms. 2Application: The fuel level sensor supports Marine, Rv, and truck oil level gauges and tank level gauges, with washers and mounting screws to prevent the sensor from touching the bottom of the tank. 3Installation Suggestion: If the fuel tank is plastic, the length of the gas tank level sensor should be 1in/2.5cm smaller than the depth of the fuel tank, if it is metal, the length of sender should be smaller than the depth 0.5in?1in/1.25?2.5cm. 435mm Float: The float is 1.38in (35 mm) in diameter. If a hole must be drilled, a 1?1/2in (38mm) diameter hole would be perfect. The sender has a nonlinear output that can only be matched with a standard meter with a nonlinear signal. 5Long Durability: The advantage of this doughnut float type level sender over a thick film swing arm type level sender is the durability and reliability of the reed switch. No need to adjust the tank.