The Fotasy M39 to M42 Adapter Ring Set includes two high-quality adapter rings designed to allow M39 mount lenses to fit onto M42 screw mount camera bodies. Crafted from durable all-metal materials, these rings ensure a secure and stable connection for your photography needs. While the physical fit is seamless, please note that automatic diaphragm and auto-focusing functions will not operate when using this adapter. Ideal for photographers looking to expand their lens compatibility.