I am focusing for visual observation. Problem is that the standard 2" adapter would provide this extra 40mm but i cannot use it because the inner diameter of the nose of the tube is a bit below 2" , which leads to my barlows and filters hitting it. The skywatcher focuser is designed to be too short, and you need to use a 1.25" adapter or a 2" adapter to reach visual focus. This makes focusing cameras etc. easier since you can just remove the adapters. I just hate those adapters with thumb screws so I have a 2" to 1.25" compression ring adapter with 2" filter threads , and a m54->2" adapter for the focuser. What I now need to get the perfect solution is the 40mm focuser extension M54 to M54 so I can move the M54 -> 2" adapter a bit outwards so it is in the middle of the focuser travel. This way I will have a nice 2" tube with no obstructions which i can drop down to 1.25" with a single adapter. This will also give me the possibility to screw 2" filters into the 2" -> 1.25" adapter so I can use my 1.25" eyepieces and barlows without having to constantly move the filter.