This is a mount adapter for attaching M42 mount lenses to Canon EOS EF cameras. (M42 mount lens → Canon EF mount conversion) For those who use old lenses. ・Allows the use of all M42 screw mount lenses on Canon EOS cameras. ・Easy to install with a smooth surface. Durable anodized aluminum construction. ・Supports aperture priority and manual modes. You can use your mount lenses on Canon EOS/EF camera bodies. Recommended for those who prioritize cost performance.