Want the custom AR-15 and Large Format AR (LFAR) experience with Drop-In convenience? Well this barrel is up to the job. Each barrel is machined using the same processes that have helped Shilen customers win endless competitions and set numerous World Records over the years. Using Shilen's pre-threaded blanks each barrel is assigned a bolt assembly and then chambered to the correct headspace for THAT bolt. Gas-block shanks are machined to +- .001 for proper fit. Each barrel is uniquely numbered to match with its corresponding numbered bolt and the barrel extension is installed. (Gas block and gas tube not included. If you have a standard factory style open sight gas block it will require additional machining for cross pin alignment).