You know the situation - you've clamped your precious eyepiece using the locking screw on the focuser. But instead of sitting precisely in place, it is tilted or even worse - the screw marks and damages the barrel. But this doesn't need to happen, there is a solution: the Twist-Lock adapter. Put your 1.25" eyepieces or other accessories one: Turn the lock-ring and your eyepiece now sits firmly anchored in place. Your eyepiece no longer needs its safety groove as the adapter now clamps it over a large area of around 15mm. You can also use the 2 "to 1.25" adapter as a permanent 2" barrel for example. Suppose you are observing with some 2" eyepieces but also have a favourite 1.25" eyepiece you want to use. Instead of constantly having to fiddle around with adapters, you could simply use this adapter together with the eyepiece and use it with a fixed 2" barrel.Save money when buying filters - A 2" filter thread offers the option of using a 2" screwed filter, even when using a 1.25" eyepiece.