USED SLR Sentry 8 .875 Adjustable Gas Block w/.400 in. Set Screw Spacing Black SA8-SM. 400 inch Set Screw Spacing. 15-position adjustability from 0 - 0.125 inch port opening. Metering screw and screw bore design allows repeatability and reliability only SLR has been able to deliver. Single tool click to adjust gas metering. Melonite finish 4140 Nexturn Swiss precision metering screw. Proprietary Alloy Flat Spring with 1400deg temper. Melonite finish 4140 detent plunger. USES STANDARD GAS TUBE. Included Accessories: Tool roll pin and mounting screws Specifications for SLR Sentry 8 .875 Adjustable Gas Block w/.400 in. Set Screw Spacing: Manufacturer: SLR Coating: Melonite QPQ Finish Gas Block Journal Size-Diameter: .875 in Gun Make: AR Platform Additional Features: w/.400 in. Set Screw Spacing Gas System Type: Direct Impingement Features of SLR Sentry 8 .875 Adjustable Gas Block w/.400 in. Set Screw Spacing: .400 inch Set Screw Spacing. 15-position adjustability from 0 - 0.125 inch port opening. Metering screw and screw bore design allows repeatability and reliability only SLR has been able to deliver. Single tool click to adjust gas metering. Melonite finish 4140 Nexturn Swiss precision metering screw. Proprietary Alloy Flat Spring with 1400deg temper. Melonite finish 4140 detent plunger. USES STANDARD GAS TUBE. Included Accessories: Tool roll pin and mounting screws Package Contents: SLR Sentry 8 .875 Adjustable Gas Block w/.400 in. Set Screw Spacing SLR SA8-SM: Sentry 8 .875 Adjustable Gas Block w/.400 in. Set Screw Spacing Black