I have used these brushes for a year or so. They are good, quite thin but stiff wires which I like and adjustable.
But... The wires don't fully retract into the handle, a few millimeters stays sticking out which meant they are vulnerable to damage in the stick bag. I kept finding wires with bent over ends. In the end I got some metal shears and trimmed about 5 mm off the ends, cleaning up the bent wires and allowing them to fully retract.
Also, if retracting then a bit too vigorously it is easy the pull the rubber cap of the end and the wires come right out with the handle. You can put them back in, a bit fiddly, but you don't want to be trying to do that whilst the band leader is counting in the song...
And lastly, there is no rubber coating, the shaft is just an aluminum tube and it is quite thin. They feel a bit too thin for me.