The Baader Planetarium 1¼"/2" Expansion Adapter enables use of 2" eyepieces in 1¼" focusers and diagonals (of course some vignetting will occur with larger 2" eyepieces). The 1¼" Nosepiece is threaded for 1¼"filters and the internal surfaces are fully baffled to control stray light reflections. Optical path length is 49mm The expansion adapter's modular construction permits other uses. The 1¼"Nosepiece may be removed to expose an internal T-2 photo thread enabling connection to all the other Baader Astro T-2 accessories. Also the T-2 threaded ring may be removed to expose a 2" SCT thread.