Base (long side) x Sides x Thickness Approx. 25mm x 18mm each x 12.5mm 2 pieces These are Porro prisms used inside binoculars. They have a unique shape, like the corners of an isosceles triangle have been shaved off. Unused, stored at home. No scratches or chips are visible to the naked eye. We will deliver items of the same quality as the photos. They can be used as teaching materials for crafts and light refraction experiments, processed into accessories, or used as interior decorations. A rainbow appeared when exposed to sunlight. They would be good for science projects or as good luck charms. The size and condition are amateur assessments, so they may differ slightly from the actual product. Please understand this beforehand. Although unused, there may be slight deterioration of the surface coating due to long-term storage. I don't know what effect it would have if the coating peeled off when assembling binoculars, but it should be fine for viewing. We are looking forward to your purchase if you don't mind. We have other sizes of prisms, so if you want multiple pieces, please comment before purchasing. You can search here ↓ #BinocularPrism If you are looking for triangular prisms or glass accessories with a unique shape, how about this opportunity? Summer vacation For science projects Optics Binocular parts Glass Homemade Telescope Monocular Binoculars Magnifying glass Rainbow Dah (roof prism) DH