Description This product is a M42 to RMS adapter. It is made of materials. It is safe and durable. It can serve you for a long time without being easily damaged. It is an excellent M42 to RMS adapter that can bring you convenience, allowing you to have a more comfortable experience. Features -Color: Black -Material: aluminum alloy -Size: 4.00X4.00X0.40cm/1.57X1.57X0.16in Outer diameter: 4cm Inner diameter: 2cm - This adapter ring is fit for microscope objective lens with RMS threaded interface. - Smooth surface, easy installation. Sturdy anodized aluminum structure. - The bellow can be used. The maximum distance of the microscope objective lens is 160mm, that is, the back focus of the bellow and SLR interface should be less than 160mm. - Lightweight and portable, reducing the thickness and weight of the adapter ring. - Simple in structure, easy to use, not easy to deform, you can use it with confidence. This adapter ring is fit for microscope objective lens with RMS threaded interface. Smooth surface, easy installation. Sturdy anodized aluminum structure. The bellow can be used. The maximum distance of the microscope objective lens is 160mm, that is, the back focus of the bellow and SLR interface should be less than 160mm. Lightweight and portable, reducing the thickness and weight of the adapter ring. Simple in structure, easy to use, not easy to deform​, you can use it with confidence.​