Truly the first brush to clean the AR-15 6.5 Grendel Chamber. They are sized to close tolerance for precision cleaning. Made out of a distinctive blue Nyflex fiber, which is thick, stiff and holds its shape well and allows for back and forth action unlike traditional brass and bronze type brushes. They may be used several times before becoming worn. The brushes are wound tightly so there is more cleaning area per inch, and the shank is a solid construction, sized to fit 8/32” cleaning rods.