Unicorn 3B — Mushroom Substrate Fruiting Bag (Large) *high gas exchange*

The Unicorn 3B is a large mushroom substrate fruiting bag built around the breathable B filter — the choice for growers who need maximum gas exchange during colonisation. The same trusted bag dimensions as the 14A, but with a 5 micron B filter that promotes faster, freer air exchange. Made in the USA since 1990 by Unicorn Bags LLC, the industry's most trusted name in mushroom cultivation bags.

Specifications

• Filter: 5 micron B filter — high gas exchange, promotes fresh air exchange for species sensitive to CO₂ build-up
• Capacity: Up to 5 lbs (~2.3kg) of substrate
• Size: 19" × 8" × 5"
• Material: 2.5 mil polypropylene — autoclave and pressure cooker safe at 121°C / 15 PSI
• Side-gusseted, reinforced bottom seal

Why Growers Choose the 3B

• The B filter's 5 micron pore size delivers high gas exchange — ideal for species that need strong fresh air exchange and are sensitive to CO₂ build-up
• Same trusted dimensions as the 14A in a slightly lighter 2.5 mil polypropylene construction
• 2.5 mil polypropylene handles autoclave and pressure cooker cycles without warping or seal failure
• Trusted by hobbyists + commercial growers worldwide

Prefer a more balanced gas exchange option? The 14A uses a 0.5 micron A filter for versatile use across the widest range of species. Ready for more volume? The XLS-A is built for high-volume production.

Need grain spawn bags instead? See our spawn bag range.

The 3B is the bag of choice when high gas exchange is the priority. In stock & dispatched quickly from our UK warehouse.