High-quality material: The expansion ball is made of black rubber, the white screw with solid brass threads inside is made of nylon, the long screw and washer are made of 304 stainless steel, and the soft washer is made of ABS plastic. Durable, rust- and corrosion-resistant, superior to most plastic devices. Size: The detailed size of each toilet seat nut is shown in the picture. Please measure before purchasing to ensure your toilet seat works properly. Rust-proof design: Plastic washers will not rust, better than metal washers. When you tighten the bolt, the washer pushes into the hole, and you must be careful not to overtighten the bolt so that it passes through the washer. The screws have solid brass threads in a non-slip, rust-resistant case. Easy to use: Insert the toilet seat bolt into the toilet seat mounting hole. The grommets have a threaded section, so you simply screw them into the hole at the top of the toilet. When you tighten the screw, it expands and tightens in the hole. No need for a bolt on the other end. Convenient and time-saving. Universal: 2 pairs/4 pieces toilet seat replacement parts kit. If your toilet seat keeps moving, use these toilet seat fixing screws to replace the useless plastic insert that came with your new fixed top seat. The toilet seat connector fits most standard toilet seats with fixed top hinges.