Thought I would just share my recent find when I was trying to line up CCD with OAG . Baader make these pack of 15 T2 spacers of various thickness
to help get you all lined up straight and also act as a washer to stop those
metal to metal surfaces from sticking .
I got these off ebay .
That sounds about right I wasn't to concerned about the actual measurements myself as it's just trial and error as to what thickness will work as it's probably different for everyone but the quality is better than I expected.