Atrius Development X Series Forced Reset Selector Black. The latest addition to the FRS family which features a new trip system that has a trip base and trip clutch to allow for a universal fitment amongst gas piston platforms. The Atrius Development Group FRS X-Series was designed to be compatible with a variety of Sig Sauer MCX MPX Rattler platforms and even Sig's MCX-Spear LT Upper AR Conversion Kit. Specifications for Atrius Development X Series Forced Reset Selector: Manufacturer: Atrius Development Color: Black Finish: Heat Treated Gun Make: SIG Sauer Gun Model: Sig Sauer MCX-Rattler Sig Sauer MCX-SPEAR LT SIG Sauer MCX SIG Sauer MPX Fabric/Material: 4140 Steel Hand: Ambidextrous Features of Atrius Development X Series Forced Reset Selector Style: Atrius Ambi Selector Switch (original design) Configuration: Safe Semi Super-Semi Includes a new FRS lever with dimension compatible for MCX/MPX product lines Universal design for Sig Sauer gas piston platforms Installation: Drop-In Ready (No Modifications Necessary) Package Contents: Atrius Development X Series Forced Reset Selector What firearm models does the manufacturer say Atrius Development X Series Forced Reset Selector is compatible with? The manufacturer suggests that Atrius Development X Series Forced Reset Selector is compatible with SIG Sauer MPX SIG Sauer MCX Sig Sauer MCX-SPEAR LT Sig Sauer MCX-RattlerAtrius Development ADG-FRS-AMBI-X: X Series Forced Reset Selector Black