The Baader T2 fine adjustment rings are available in five sizes, 0.6; 0.8; 1.0; 1.2; 1.4 mm wall thickness.
For some of the T2 accessories, due to manufacturing technology, a small groove is created at the end of the "father" thread into which the thin ring can move laterally. As a result, the CCD cameras can also tilt the image plane minimally, which can lead to star degradation at the corners.
The tight fit of the Badder T2 fine adjustment rings means that the ring cannot slip into the groove on the T2 accessories, so there is no tilting of the image plane. The rings are made of plastic, precisely so that if they can't be slipped onto an accessory, they can be easily cut at one point with scissors and easily put on and taken off when slightly opened.