Volquartsen Firearms Extended Bolt Release for MKII and MKIII Black. 375" serrated face for an easier release of the bolt. Fits both the Ruger MKII and MKIII. Not compatible with the 22/45. Specifications for Volquartsen Firearms Extended Bolt Release for MKII and MKIII: Manufacturer: Volquartsen Firearms Gun Model: Ruger Mark III Ruger Mark II Country of Origin: USA Package Contents: Volquartsen Firearms Extended Bolt Release for MKII and MKIII What firearm models does the manufacturer say Volquartsen Firearms Extended Bolt Release for MKII and MKIII is compatible with? The manufacturer suggests that Volquartsen Firearms Extended Bolt Release for MKII and MKIII is compatible with Ruger Mark II Ruger Mark IIIVolquartsen Firearms VC2BR-B: Extended Bolt Release for MKII and MKIII Black