Egw scope base mossberg 500 picatinny rail w/#6 screws FEATURES:-Machined from 6061-T6 extruded aluminum-Matte black finish-For Mossberg 500 (Post-'97)-Center Spread: 2.125"*-Overall Length: 5.882"-Mounting Hardware: Hex head screws & wrench provided-Installation: EGW recommends 20 inch lbs. of torque & a drip of blue Loctite*The center spread is the distance between the two middle holes, center to center, on your receiver. Other Features: Made in usa for late (after 1997 mfg) mossberg 500/590/835/930/935