Excellent Material - Black Rubber (expandable ball) / ABS Plastic (round cards) / Stainless Steel (screws). Made from strong metal hinges and bolts, better than most plastic fixtures. Rubber Bungs - The rubber bungs slide into the holes perfectly and when you tighten the bolts they squash up in the holes to make a good tight fit. Non-rust Washer - Supplied with 4 soft plastic washers. Plastic washers will not rust, better than metal ones. When you tighten the bolts the washers crush down into the holes, you need to be careful not to tight the bolt so much it pushes through the washer. Threaded Design - The rubber grommets have a threaded section so you can just push them into the holes in the top of the toilet pan and when you tighten the screw it expands and tightens itself into the hole, without the need of a bolt on the other end of the screw. Universally Fit - Expansion ball diameter: 1.8 cm/ 0.7 inch (unexpanded state). Length: 4cm/1.57 inch. Suitable for 14-16mm hole for 2 toilet seats. Great for broken or old toilet seat hinges. Fits for most standard toilet seats with top fix hinge.