Amazon.com : Telescope Barlow Lenses Kit 2X-3X-5X, 1.25 Inch Telescope Accessory, Fully Metal Multi Coated Broadband Green Film Barlow Lens for Telescope Astronomy Eyepiece : Electronics
What is a Barlow Lens? - YouTube
SVBONY Telescope Eyepiece Set with 2x Barlow Lens 4 Element Plossl Design 6.3mm 32mm 40mm