The Williams™ WGOS-26mm Open Sight Less Blade 31793 is ideal for mounting various open sight configurations on a variety of firearms. Using the measurements below you can easily select the correct size for your gun. Please note that some firearms may require drilling and tapping to accommodate the Williams™ WGOS-26mm Open Sight Less Blade 31793 as the sight uses two 6X48 screws to attach the base to the blade.