This is the bag I use for 3-4lb grains and 5lb AIO's. 

Type: Gussetted

Material: 3.0 Mil Polypropylene

Bag Size: 5″ X 4 X 18″

Filter Type: T

Filter Size: 1.5″X1.5″

Filter Pore Size: 0.2 microns

Filter Hole: Style L