This rail system offers two 3-slot picatinny rails for Mossberg 590/590A1/Shockwave 12-gauge firearms.  This kit includes a rail system machined from solid 6061-T6 billet aluminum and a steel swivel screw.  Both items are coated with color-matched Cerakote ceramic coating to match the firearm's factory finish and for increased durability.  Attaches over the magazine cap for an easy 30-second installation.