Amazon.com : NEEWER 2X Barlow Lens for Telescope Eyepiece, 1.25” Multi-Coated Metal Lens to Double Magnify Eyepieces with M42 Thread to Connect to DSLR or SLR Camera : Electronics
2X Barlow Lens For SM and SW Stereo Microscopes (48mm) – AmScope
Amazon.com : SVBONY 2X Barlow Lens 1.25 inch Double The Magnification Multi Coated Broadband Green Film Telescope Accessory with M42 Thread : Electronics
Amazon.com : SVBONY 2X Barlow Lens, Doubles The Magnification Telescope Barlow Lenses, 1.25 inch Multi Coated Broadband Green Film Telescope Accessory with M42 Thread for Standard Telescope Eyepiece : Electronics