This item is manufactured with premium plastic for durable and long lasting use. It is great for variety of uses such as loose-leaf, memo filing and sample holders. These rings are two holes to fix in, not like other metal rings, without any strength they can be easily install. Will not hurt your hands or children's hands. Feature- Color: Colorful.- Material: Plastic. - Size: 3.50X3.50X0.40cm/1.38X1.38X0.16 inch. - Inner diameter: 28mm/1.1 inch. - Made of plastic, the loose leaf rings are durable and won't crack or split.- The book rings are great for variety of uses such as loose-leaf, memo filing and sample holders.- Easy to use: Pull to open, squeeze to close, lock for additional security.- Wide Application: These plastic binder leaf rings are perfect for documents orgainzation and ssorting. Different color present the level of importance. Also suit for children learning cards sorting. - Easy to use: First find the seam on the book circle, then use your fingers to separate it in the opposite direction, then squeeze to close it.