Bosch Wire Pencil Brush Steel Wire/Nylon Shank Ø 6mm - Bosch 2609256538, The wire pencil brushes from Bosch are supplied in sizes from 10 to 25mm and with either nylon or steel wire.
They all have a 6mm shank.
Bosch 2609256538 Wire Pencil Brush Ø 25mm Steel Wire Shank Ø 6mm