C-mount to T-mount adapter ring

Adapter ring from T-mount (M42x0.75) to C-mount (25.4mm)
On one side, M42x0.75mm male thread. On the other, female internal thread (25.4mm).
This ring is generally used to mount a large sensor camera (T-mount) on a guide port (C-mount).
To be used with C/CS ring if required.
To find out all about the different mountings and threads, read this article.