Here at AR15Discounts.com we work with a wide variety of machine shops and barrel manufacturers. When we come across a barrel maker we like, we will often decide to private label those barrels for resale under the NBS brand. We purchase these barrels in large quantities and then pass the savings on to our customers.Why buy an NBS Brand Barrel: American Made - Sourced from a variety of Tier 1 Manufacturers here in the United States Quality Control - All barrels are manufactured under ISO-9001 or better quality standards Best Value for the MoneyMAY OR MAY NOT COME WITH THREAD PROTECTOR, DEPENDING ON AVAILABILITY. DISCLAIMER: This product is not manufactured, authorized, endorsed, or warranted by GLOCK. GLOCK does not warrant or represent that this product is compatible with GLOCK pistols.