LPL lens board for enlarging lenses with 39 x .75mm mounting thread, often referred to as "39mm fine". This is the thread used on #1 shutters so is often found on lenses in barrel mount, such as older Schneider Componon 150mm lenses. This lensboard is not suitable for lenses with the more common 39mm "Leica" thread, which has a different pitch. Please check the mounting thread of your lens. The lensmount is threaded, so no retaining ring or mounting flange is required.