The Mystic Precision T-Slot Rail mounts to you're stock, allowing you to mount your Mystic Precision MPOD for accurate, F-Class ready shooting. Short length: 3.596", Long length 4.595". Note: These mounts require two holes in the stock or use of dual stud inserts. The Long T-Slot Rail has spacing to fit holes 2.5" to 3.6" center to center. The Short rail supports hole spacings between 1.5" and 2.6."