This is a ProMag Stock known as the Archangel, model 556R.
AA556R Easily installed on your Ruger 10/22(R)" the ARCHANGEL AA556R adjustable six-position stock features a drop-in fit that requires no gunsmithing. Proprietary carbon fiber filled polymer construction will ensure a lifetime of hard use. Makes your Ruger 10/22(R) mimic the look and feel of an M-4 carbine. It has a 6-position buttstock and 4 quick detach sling swivel hard points. There is a full length top picatinny rail and a 6 o'clock Picatinny rail on the forend. The forend sides are slotted for the addition of optional Picatinny rails and the collapsible M4 style stock adjusts from 7" to 11" length of pull. Includes an extended magazine release.
Ergonomic pistol grip w/finger grooves
Muzzle attachment allows attachment of gas-block height sights on OEM barrels
Includes extended mag release