This is a 3D-printed adapter for mounting L39 mount lenses on M mount bodies. The material is PETG, which is lightweight and durable. This set includes two adapters: one for 28mm lenses and one for 90mm lenses. Other combinations are also available: 35mm / 135mm 50mm / 75mm If you would like to combine different types, please let us know in a message when you purchase. This product is manufactured using a 3D printer. Therefore, there may be some layer lines or roughness on the surface. Production may begin after your order is placed, and it may take some time to ship. Thank you for your understanding.