Description: M52 to M42 Focusing Helicoid Ring Adapter Macro Extension Tube Three styles to meet your needs. This tube useful for lens without focusing ring or for mofify lens purpose. It can be use as macro extension tube. There is no electronic element in the adapter, aperture and focusing must be manually control. Material : High quality and compact. Made of aluminum alloy, 100% Brand New. Specification: Size: Approx. 6.3x6.3x3.5cm/2.48x2.48x1.37inch Front mount: M52 screw mount female Rear mount: M42 screw mount male 17-31mm Length: 17mm to 31mm (14mm movement distance for focusing) 25-55mm Length: 25mm to 55mm (30mm movement distance for focusing) 36-90mm Length: 36mm to 90mm (66mm movement distance for focusing) Focus: manually Material: aluminium alloy Package Includes: 1 x M52 to M42 Macro Extension Tube Note: 1.Please allow 1~3 cm error due to manual measurement, thanks. 2.Due to the difference between different monitors, the picture may not reflect the actual color of the item. Please understand, thank you.