Catalyst Arms states that it fits: AR-15 gas guns (with low profile block) Ruger Precision Rifle – Short action (Gen I, II, & III)
For ease of installation Fast Track™ attaches to both AR-15s and Ruger Precision Rifles via a two barrel nut system that is easy to align and torque to proper specification.
They also note: When installing on Ruger Precision Rifle, installation does not require removal of barrel nut to install. Installation will not affect precision of your barrel/receiver combination.