50 QTY Small Size 4'' x 3'' x 18'' Sealable Spawn / Myco Bags With 0.5 Micron Filter Designed for Mushroom Cultivation Growing Bag Size is 4 x 3 x 18 Inches. 0.5 Micron Filter 3.0 Mil Polypropylene Can Hold 2-3 Pounds of Substrate