Astrodymium Colour Coded Fine Tuning Spacer Rings for M42/M48/M54 Threads

AstrodymiumSKU: M42-CC-SR

Size: M42 (12x)
Sale price$17.99
In stock


These rings slip over the thread of an adapter/extension tube, and are primarily used for fine tuning backfocus when doing astrophotography, but they can be used for other purposes as well.

Also available on Agena Astro (United States) and First Light Optics (UK / Europe)!


M42 & M48 contains 12 individual spacer rings, with 3 different thicknesses. 4 of each thickness is included: 0.4/0.6/1.0 mm.

M54 contains 9 individual spacer rings, with 3 different thicknesses. 3 of each thickness is included: 0.4/0.6/1.0 mm.


Each ring is also colour coded for easy identification.

  • Red - 0.4mm
  • Blue - 0.6mm
  • Black - 1.0mm

Each ring has an inner diameter that is 0.5mm larger than the specified size, for good clearance on the threads - They will not get stuck and are easy to insert or remove. 


This item is made out of UV resistant PETG plastic and can handle up to 80C (176F) temperatures without deformation.

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Customer Reviews

Based on 1 review

I used this to achieve the correct backfocus. I like that they are color coding

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