Review on 🧴 Bottle Jack/Floor Jack Oil Reservoir Rubber Filler Plug Bung, 12PCS - Horizontal Jack Bung for Hydraulic Jack Oil Reservoir Filler Hole, 8mm by Justin Garcia

Although I initially thought the plug would not fit, it just takes a bit of work to get it into the filler hole. I had to push with a screwdriver. The part you insert is tapered, that helps. Of course they have to fit snugly. Tip: Do not overfill the jack with hydraulic fluid. I did, and with enough pressure, the cork burst and a fair amount of liquid from the socket.