Nylon brushes are unaffected by most modern solvents and won't deteriorate from exposure to the harshest chemicals. Includes brushes for 17, 22, 243, 25, 6.5mm, 270, 7mm, 30, 8mm, 338, 375, 416 and 45 calibers. All brushes have standard 8 x 32 male threads except the 17 caliber brush which has 5 x 40 male threads. Packaged in a durable, hinged plastic box with marked slots. 14 piece set Rifle Bore Brush Set.