Variable locking T-2 extenison (12 - 14 mm optical length)
A great value 'Bundled' combination of the following Baader items:
T-2 Conversion Ring (10mm length) #2958110
T-2 Locking Ring (2mm length) #2958120
T-2 / T-2 Inverter #1508025
Screw the two larger rings with T2 thread into each other until you reach the correct length, then lock with T-2 locking ring. This is adjustable to the exact mm length, and as with all Baader T-2 systems, many T-2 accessories are compatible.