Nylon will not harm your barrel. Tightly wound precision brass core brushes effectively remove fouling from gun barrels.

• Industry standard 8-32 male thread (5-40 for .17 Cal. & .204 Cal.)
• 5/16-27 male thread (12,20,28 & 410 Gauge)
• Close tolerance specifications for perfect bore fit
• Will not harm or scratch steel
• Durable and reusable