121mm 延長管，用於3吋FT調焦器 (STE-M109-121)

The threads on this extension are incredibly smooth—it screwed right onto my 3" focuser without any binding. It’s exactly the 121mm I needed to fix my back focus issues for my imaging setup.

This 121mm extension gave my imaging train exactly the spacing it needed without any wobble. The threads are smooth and precise, making it straightforward to attach to the focuser. It’s a solid, well-made piece that solved my back focus issues instantly.

The threads on this extension tube are buttery smooth and mated perfectly with my 3" focuser, giving me the exact 121mm of back focus I needed for my imaging train. No wobble or play at all once tightened down.