This Blue Fireball adapter allows you to attach 1.25" eyepieces and accessories to any equipment/adapter that has a male T thread (T2 mount). Common examples are telephoto lenses (which can be converted into excellent finder telescope with the use of this adapter, spacers, and an eyepiece), T thread adapters, off axis guiders, etc. Some Maksutov-Cassegrain telescopes use a male t-thread on their rear cell, so you can use this adapter as a 1.25" visual back for such scopes.
This high quality adapter has a T2 female thread on one end and a 1.25" eyepiece barrel on the other end. Eyepiece barrel features brass compression ring. Made of black anodized aluminum. Total length = 29mm (1.14").Blue Fireball part number: E-10