USED Volquartsen Firearms Extended Bolt Release for Ruger MK IV Black VC4SR-B. This extended bolt release gives you more surface area and deep serrations for easy thumb engagement. The bolt release pad is CNC machined from 416 stainless and extends .050" further than the factory release. This .050" extension combined with the improved ergonomic flat design of this release is an improvement that every target shooter is looking for.Not compatible with 22/45 pistols. Specifications for Volquartsen Firearms Extended Bolt Release for Ruger MK IV: Manufacturer: Volquartsen Firearms Gun Model: Ruger Mark IV Fabric/Material: 416 Stainless Steel Country of Origin: USA Package Contents: Volquartsen Firearms Extended Bolt Release for Ruger MK IV What firearm models does the manufacturer say Volquartsen Firearms Extended Bolt Release for Ruger MK IV is compatible with? The manufacturer suggests that Volquartsen Firearms Extended Bolt Release for Ruger MK IV is compatible with Ruger Mark IVVolquartsen Firearms VC4SR-B: Extended Bolt Release for Ruger MK IV Black