Size: Expander ball diameter: 1.8cm (unexpanded state). Length: 4cm. White screw size: 4.5 x 0.5cm. Nylon expander nut size: 3.7 x 1.8cm. Washer diameter: 1.4cm. (The detailed size of each toilet seat nut is in the picture, please measure before purchasing to ensure your toilet seat works well) Excellent material: The expander 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 ABS plastic. Sturdy and durable, rust-proof and corrosion-resistant, better than most plastic fasteners. Anti-rust design: Plastic washers will not rust, better than metal washers. When you tighten the bolts, the washers crush 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 which can be slip-resistant and rust-proof. Easy to Use: Place the 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 itself in the hole, without the need for a bolt on the other end of the screw. Convenient and time-saving. Universal: 2 pairs/4 pack toilet seat replacement parts. If your toilet seat keeps moving, please use these toilet seat fixing screws to replace the useless plastic inserts that come with a new Top Fix seat. Fits most standard toilet seats with top-mounted hinges, toilet seat hole 14-18mm. Quantity: 2 pairs / 4 pieces.  Note: Other items are not included, the color is based on the first picture, and other pictures are for effect only. Due to the differences between different monitors, the picture may not reflect the actual color of the item. Due to manual measurement. Please allow deviation. Thank you!becomeveryrich