This is still your favorite compact firearm with the same reliability enhancing technology, but the pdx 505-sps features maxim's scw pistol system in place of the scw stock or brace.The scw pistol system is their most streamlined option for the back end of an ar pistol.No protruding angles and nothing to get caught on.At just 5.3 ounces, the scw pistol system shaves over 10 ounces when compared to our scw stock.It includes a rear single point qd swivel mount, an ideal placement when using a sling for accuracy-aiding shots down range.Action: Semi-AutoCaliber: 5.56x45mm NATOBarrel Length: 5.50"Capacity: 20+1Grips: Arid Brown PolymerSights: None, Optic ReadyWeight: 5.10 lbsStock Material: SyntheticOal: 18.75"Barrel Length Range: 5" to 5.99"Weight Range: 5 lbs to 5.99 lbs