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Amazon.com : Astromania Bahtinov Mask Focusing Mask for Telescopes - FM60mm for a Tube Outer Diameter (OD) from 65mm-100mm - can be Mounted with The Brass Screws Inside or Outside The drawtube :
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Astrozap Focusing cap w/ built-in Bahtinov focusing mask for 11" Schmidt-Cassegrains and similar scopes | Astronomics.com
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High Precision 16 Line Bahtinov Focusing Mask in Different Diameter Acrylic Focusing mask for Astronomical Telescope Photography| | - AliExpress
![Bahtinov Mask Focusing Mask for Telescopes FM200mm for a Tube Outer Diameter OD from 215mm260mm can be Mounted with The Brass Screws Inside or Outside The drawtube - Newegg.com Bahtinov Mask Focusing Mask for Telescopes FM200mm for a Tube Outer Diameter OD from 215mm260mm can be Mounted with The Brass Screws Inside or Outside The drawtube - Newegg.com](https://c1.neweggimages.com/ProductImage/AP81D200806X6HWH.jpg)