I've just fitted these (blue ones).
Been in the garage for longer than I care to remember; fitted them to my medium mixed 0 degree, Gardiners brush.
Best fan jets hands down.
I don't think I'd trust them in a soft brush as I'd be afraid of plastic body of fan gets scratching glass.
(the design of these fan jets makes them protrude 5 plus mm from brush stock.
Where as Gardiners fan jets hardly protrude at all.