Right then….
First of all, some of the following has been gleaned from previous threads, both here and elsewhere, so credit to you if you recognise something you’ve posted previously.
I’ve got a set of Magura Louises and this adapter fits the calliper (even though it says rim brakes). It’s M6 thread so you can check if it would fit yours. For the lever it’s just a friction fit of the syringe end.
For Avid you need something like this (M5 thread A344-4.5-M5 or A345-4.5-M5). The threaded bit is actually a bit shorter than ideal. I have a set of Juicy 3’s and a set of Juicy 5’s. The lever on both is the same and sloping so you need to cut the hexagonal nut part back a bit. The caliper on the 5’s is a bango and perfectly flat so the adapter fits perfectly. The caliper on the 3’s has a ridge so also needs a bit of the hexagonal nut part cut a bit. How do you cut the hexagonal parts back easily? Simple, in a lathe or, of you haven’t got a lathe in your tool box, something very similar – an electric drill.
Right, off to the pub now. May add a bit when I get back.