The astro essentials ones are more expensive and you may need more than one pack, but they are worth it. These baader ones have too small an internal diameter and can get very solidly stuck on your threads. I spent a long time trying to pry one off. They also do not come in labelled bags, all the different sizes are loose! The astro essentials ones came in bags labelled "1.2", "0.8", "0.5" etc. They fit properly, and are made of a nice coated metal instead of plastic.

I bought a set of these washers to provide some give when tightening the T-2 threads of my diagonal and filter wheel and to set the orientation of one part with respect to the other (by changing the washer thickness). The washers fit perfectly to all my Baader and ZWO T-2 connectors, there is no play, but they fit over the threads without forcing.

I’ve been using these for a while and while it is indeed the case that they are too tight the matter is easily solved by cutting them: this does not affect their operation and makes it easy to add and remove them.

These do what I need them to do. As commented by some others, these are tight on the threads, particularly the thicker spacers. I did find, however, that putting them into hot water for a couple of minutes made it much easier to fit them.

Quite poor. The inner aperture wouldn't go over a T2 thread unless forced. Good range of thickness' is about the best I can do on these.

They seem to be of setting size. Do not 'slip over' T2. It's been an absolute waste. I broke a ring while trying to insert over a t2 thread, so guess can't return as well.

The tolerances on these items are very good meaning I can sort the spacing out, but the ones I received far from "slip" over T2 threads - requires a fair bit of effort and very tricky then to remove later. 2/5

After years of having T-thread adapters and filters and nosepieces and spacers locking together and then defying any attempt to open them again, and after trying everything from milk bottle rings to PTFE tape to stop them sticking, these Delrin Rings from Baader offer one of those simple but beautifully effective solutions that make all the difference.
Not only do they help prevent threads locking tightly together, but they can also serve as great 1mm spacers, essential when trying to achieve correct spacing between cameras and reducers.
The spacers themselves are well made from neatly cut Delrin, and they press onto the male T2-threads quite easily, without distorting.
I have now added spacers to every T-thread accessory I have, they work so well they should probably be standard issue, definitely a must have item for anyone using T-Thread fittings. I only wish I'd found them years ago!