Size: Black expansion ball diameter: 1.8cm (unexpanded state). Length: 4cm. White screw size: 4.5 x 0.5cm. Nylon expansion 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 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, 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 for anti-slip and anti-rust use. 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 as you tighten the screw, it expands and tightens into 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. Toilet seat fittings fit most standard toilet seats with top fixing hinges, toilet seat hole size 14-18mm. Note: The data are all measured manually, please allow 1-3cm error due to differences in light and display, there may be some color differences, please refer to the actual item received.