These are 14a filterpatch mushroom grow bags. They hold approxietly 5-6 pounds of hydrated substrate. Shipping is a $10 flat rate. (200 bags is a better deal as flat rate shipping is $13.65 for 200)
 
Manufacturer's specs:
Type: Gussetted
Material: 2.2 Mil Polypropylene
Bag Size: 8″ X 5″ X 19″
Filter Type:A
Filter Size: 1.5″ X 1.5″
Filter Pore Size: 0.5 microns
Filter Hole: Style L