Excellent material: the expandable ball is made of black rubber, the white screw with solid brass thread inside is made of nylon, the long screws and gaskets are made of 304 stainless steel, the soft washers are made of made of ABS plastic. Sturdy and durable, anti-rust and corrosion resistant, better than most plastic fasteners. Anti-rust design: plastic washers do not rust, better than metal washers. When you tighten the bolts the washers squeeze into the holes, you need to be careful not to tighten the bolt so much that it pushes through the washer. The screw has a solid brass thread inside that is non-slip and rust-proof. Easy to use: Place the toilet seat bolts into the toilet mounting holes. The rubber grommets have a threaded section so you can simply push them into the holes in the top of the toilet bowl and when you tighten the screw it expands and tightens in the hole, without the need for a bolt on the other end of the screw. Convenience and time saving. Universal: If your toilet seat continues to move, please use these toilet seat fixing screws to replace the unnecessary plastic inserts that come with a new seat top fixing. Toilet seat fittings fit most standard toilet seats with top fixing hinges, toilet seats hole 14-18mm.