Maximum contamination defense in a compact format. The 4x3x18 grow bag with 0.2 micron filter is built for cultivators who prioritize contamination control above all else — smaller grain batches, contamination-prone species, environments without a laminar flow hood, and operations where protecting every bag matters more than maximizing colonization speed.
Why 0.2 Micron?
The 0.2 micron filter patch is the most restrictive commonly available for mushroom grow bags. It blocks virtually all airborne contaminants — mold spores, bacteria, environmental pathogens — providing near-sterile conditions throughout colonization. The trade-off is slightly slower gas exchange compared to 0.5 micron bags, which means colonization speed may be marginally reduced. In clean, well-managed environments this difference is minimal. In less controlled settings, the added protection is worth it.
Choose 0.2 micron when: you work without a flow hood, grow contamination-prone species, have had persistent contamination problems at 0.5 micron, or operate in a higher-contamination environment.
For most commercial grain and block production, see our 0.5 micron bags — the industry standard that balances protection with colonization speed.
Specs
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Size: 4" × 3" × 18" gusseted stand-up pouch
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Filter: 0.2 micron polypropylene filter patch
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Material: 3 MIL food-grade polypropylene (PP5) — autoclave, pressure cooker & steam sterilizer rated
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Autoclave rating: 121°C / 250°F at 15 PSI
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Capacity: 1–2 lbs of substrate
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Closure: Heat-sealable top opening
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Quantity: 25 bags per pack
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Color: Clear / translucent
Best Uses for This Size
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Small grain spawn batches — ideal for 1–2 lb rye, wheat, or popcorn loads
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Test and trial batches — new species, new substrates, or new inoculation methods
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Contamination-sensitive species — where maximum filter protection is worth the slight airflow reduction
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Hobbyist and small-scale operations — compact size fits smaller pressure cookers and limited sterilization capacity
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Grain-to-grain transfers — keeping contaminated bag risk low during the transfer process
Sterilization Notes
- Wrap the filter patch in aluminum foil before autoclaving to protect against moisture saturation
- Sterilize at 15 PSI / 121°C for a minimum of 2 hours for 1–2 lb grain loads
- The compact 4x3x18 size fits easily in most standard 23-quart pressure cookers alongside multiple bags
- Cool completely before inoculating — never inoculate warm substrate
Wholesale Pricing
25 bags per pack. Free shipping on eligible orders. Ships from the USA.
