Atrius Development Mil Spec Ambidextrous Forced Reset Selector Black. Now featuring a switch on both sides so cloners retro-builders and lefties alike can enjoy this FRS option for their next fast-shooting platform. It's the most robust solution on the market enabling the user to have 3 positions: SAFE SEMI (Traditional) and SUPER-SEMI. This Forced Reset Safety (FRS) is compatible with mil-spec/full-profile AR-15 (chambered in .223/5.56/.300 BLK) fire-control groups with no modifications required. Specifications for Atrius Development Mil Spec Ambidextrous Forced Reset Selector: Manufacturer: Atrius Development Color: Black Finish: Heat Treated Gun Make: AR Platform Gun Model: AR-15 Fabric/Material: 4140 Steel Hand: Ambidextrous Caliber: 5.56x45mm NATO .300 AAC Blackout .223 Remington Features of Atrius Development Mil Spec Ambidextrous Forced Reset Selector Style: Mil-Spec w/ Ergonomic Ridges & Pointer for Position Reminder Configuration: Safe Semi Super-Semi Installation: Drop-In Ready (No Modifications Necessary) Package Contents: Atrius Development Mil Spec Ambidextrous Forced Reset Selector What firearm models does the manufacturer say Atrius Development Mil Spec Ambidextrous Forced Reset Selector is compatible with? The manufacturer says that Atrius Development Mil Spec Ambidextrous Forced Reset Selector is compatible with AR-15Atrius Development ADG-FRS-AMBI-MS: Mil Spec Ambidextrous Forced Reset Selector Black