The Quadmag-53 is a 53 round magazine and is compatible with the Quattro-15 lower receiver. The Quattro-15's 53 round magazines give patriots the ability to carry a 210 round loadout with only 4 magazines instead of 7.
Specifications:

Caliber	5.56x45mm NATO
Capacity	53rd
Finish
Model	Quadmag-53
Material	Plastic
Type
Model Fit
Brand Fit
Capacity	53