Fotodiox Macro Focusing Helicoid - M42 Focusing Helicoid - 16MM to 30M – Fotodiox, Inc. USA
Andoer M52-M42(17-31) 17mm-31mm M52 to M42 Mount Camera Lens Adapter Ring Macro Extension Tube Helicoid Lens Focusing Adapter Ring for Macro Photography - Walmart.com
Fotodiox Macro Focusing Helicoid - M42 Focusing Helicoid - 16MM to 30M – Fotodiox, Inc. USA
Amazon.com: ASHATA M42 Lens to M42 Camera Adjustable Focusing Helicoid Ring Adapter Macro Extension Tube - Black (12mm-17mm) : Electronics
Amazon.com : Fotasy 35-90mm M42 to M42 Lens Macro Helicoid Adapter, 42mm Focusing Helicoid Extention Tube, 35mm to 90mm, 55mm Max Movement, fits M42 Screw Mount Lens : Digital Camera Screen Protector
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Pixco M39 Lens To M42 Camera Adjustable Focusing Helicoid Ring Adapter 13 -22mm Macro Extension Tube M39-m42 - Lens Adapter - AliExpress
Focusing Ring Helicoid Copal #1 DIY 4x5 8x10 Large Format Camera Lens Adapter | eBay
36-90mm M52 to M42 Manual Focusing Helicoid Camera Lens Mount Ring Adapter | eBay