A T2 thread, also written T-2, has a diameter of 42mm and a thread pitch of 0.75mm. It is also sometimes written as M42x0.75.
The low pitch distinguishes it from other M42 threads.
Baader
T2/1.25" ultrashort adapter
$ 36.90
ready for shipping in 24
h
ZWO
T2 / C mount adapter
$ 28.90
ready for shipping in 24
h
Baader
Adapter Eyepiece clamp ClickLock 1 ¼"/T-2i
$ 101.00
ready for shipping in 1-2
weeks
TS Optics
T2/SC adapter
$ 25.90
ready for shipping in 3-7
days
Askar
Adapter T2/M48 Adaptors
$ 58.00
ready for shipping in 3-5
weeks