Extra Thick bags Sealable and autoclavable, 6 mil polypropylene bags with microporous filter patches that allow gas exchange, can be used for both mushroom growing and spawn . They are widely used by mushroom growers throughout the world. We use them for mushroom spawn cultivation in our farm for a long time. You can seal them with an impulse sealer, or just tie to seal them. Those bags are durable and can be reusable in most circumstances. The integrated "self-healing" injection port allows for fast and easy inoculation with spore syringe or liquid culture syringe. Suggested Sterilization Times at 15 PSI: 5 LBS Grain Bags---120 mins 5 LBS Sawdust Blocks---150 mins Size S: 3.5" x 4" x 14" M: 5.1" x 4.7" x 20" L: 8" x 5" x 25.5"