The Geissele Magazine Well Reaction Block is designed to aid in the handling of lower receivers. The armorer mounts the lower receiver to a workbench by sliding the Reaction Block into the mag-well then clamping the Block. The Vice Block provides an ultra-stable platform for performing an array of lower receiver operations from either the top or the bottom. Quickly and easily start your MLOK nuts utilizing the integrated slots or simplify the installation of a buffer tube assembly. This tool keeps both hands of the armorer free to work, saving both time and frustration. FeaturesMade with 6061-T6 Clear AnodizeLENGTH: 6" inWIDTH: 3" in