# Key Product Features

**Dial In Precise Backfocus:** Five rings (5/7/15/20/30 mm) stack in any combination to solve spacing for astrophotography and eyepiece projection—achieve fine adjustment from 5 mm up to 77 mm total.
**True 2" Interface (M48×0.75):** Double-threaded male & female M48 on every ring for easy stacking and broad compatibility with 2" accessories that use the 48 mm filter thread (flatteners, reducers, filter holders, OAGs). *Note: M48 (2" filter thread), not M42/T-2.*
**All-Metal, Anodized Build:** Durable aluminum construction with a hard, matte anodized finish resists wear and reflections; precisely cut threads engage smoothly to help prevent binding or cross-threading.
**Maintain Optical Alignment:** Tight tolerances help keep the optical train square and repeatable when adding or removing rings—ideal for critical spacing on reducers/flatteners and camera adapters.
**QC'd & Ready for the Field:** Each set is test-assembled and visually inspected for fit and finish before packing, so you can focus on capturing sharp, high-contrast images.

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# What's in the Box

**Five M48 Extension Rings:** 5 mm, 7 mm, 15 mm, 20 mm, 30 mm
**Thread Spec:** M48×0.75 male on one side, M48×0.75 female on the other (double-threaded)
**Compatibility:** Works with 2" accessories that use the M48 (48 mm) filter thread