I wanted a better eyepiece clamp for myScoptech f12.5 acromatic refractor, this size adapter is perfect for threading on before using a compression clamp. The original clamp uses a single clamping screw that can mark the lense body.

This adapter has the "standard" Vixen 36.4mm male thread on the OTA side and a T2 or 42mm male thread on the other side. ( I combined this with a T2 Eyepiece holder.)
My old but very sharp Vixen 80M was originally made with the small 0.965 inch eyepieces, but I wanted to use it with modern 1.25 inch eyepieces.
This adapter made that easy to achieve.
Very well made as you would expect from Baader , and screws in easily.
Most 1.25 mirror diagonals and eyepieces work fine, though my erecting prism diagonal needed more infocus (prism has a longer folded light path.)

Going further to use 2inch diagonals and my Baader 2 inch Herschal wedge for solar use did mean having to shorten the scope tube a little but that was an easy fix,.