Those brush holders. Never seen, perhaps someone can explain hwo to work on them. Theres a latch on top (grey thing) which is preloaded by a leaf spring. Theres notches on the holder that you can set the grey thing into. I guess the tension will change depending where you set that. It also turns out if you open them all the way to look at brushes there's a catch keeping the things open. How convenient! But when it's time to reset it I cant find a way to release the catch, only improperly wedging something in between the catch.