Size: Black expansion ball diameter: 1.8 cm (untensioned). Length: 4 cm. White screw size: 4.5 x 0.5 cm. Nylon expansion nut size: 3.7 x 1.8 cm. Washer diameter: 1.4 (The exact size of each toilet seat nut is shown in the picture. Please measure before purchasing to make sure your toilet seat works well.) Excellent material: The expansion 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, and the soft washers are made of ABS plastic. Sturdy and durable, rust-proof and corrosion-resistant, better than most plastic fasteners. Rust-proof design: Plastic washers won't rust, better than metal washers. When the screws are tightened, the washers are pushed into the holes. Be careful not to overtighten the screw, otherwise the washer may go through the screw. The screw has a solid brass internal thread and is non-slip and rust-proof. Easy to use: Insert the toilet seat screws into the