QuickSilver Lower Unit Gear Lube Drain and Fill Hole Screw and Seal - Magnetic - Two Pack - Boat Lower Unit Gear Lube Drain and Fill Hole Screw and Seal 8M0058389 - Magnetic - Two Pack - Boat Used with 3/8 - 16 drain and fill hole screw on all mercruiser stern drives, Mercury and Mariner outboards except the veranda series. Must use this seal to properly seat The drain/fill hole screw in the lower unit. Helps prevent gear lube from leaking out and water from seeping in to the gear case causing serious damage. This is the magnetic plug screw version. The magnet imbedded in the screw plug attracts any ferrous metal shavings to keep them from suspension in the gear lube and causing damage to gears. Produced by Mercury marine to our stringent original equipment Manufacturer specifications to maximize the performance of your Mercury and Mariner outboard or mercruiser stern drive