Which BRF Jar Pack Do You Need?
Both packs contain the same half-pint jars with the same substrate, the same four-hole foil lid, and the same dry vermiculite cap. The only difference is quantity — so match the pack to the kit you're refilling.
| Pack | Best for | Notes |
|---|---|---|
| 6-Pack | Simple Grow Kit Plus owners; small batches | Matches the Simple Kit's jar count exactly. Also a low-commitment way to trial a new culture across six independent jars. |
| 12-Pack | Ultimate Kit owners; two rounds in a Simple Kit | Matches the Ultimate Kit's 12-jar capacity. Better value per jar than the 6-pack. |
| 12-Pack + 6-Pack | Mega Kit owners | The Mega runs 18 jars. One 12-pack plus one 6-pack fills the chamber completely in a single grow. |
Refilling a Mega Kit? You need 18 jars. Add one 12-pack and one 6-pack to your cart to fill the chamber in one go.
What Makes Our PF Tek Jars Different
The traditional PF Tek jar is three ingredients and one hole in the lid. We've spent more than 15 years improving on that. Four things set ours apart:
- Four foil-covered inoculation holes. Most PF Tek jars give you a single injection point, and the mycelium has to spread outward from one location. Our lids have four holes spaced around the top, so colonization begins at four separate fronts. The mycelium travels less distance, colonizes more evenly, and you can track progress from multiple angles through the glass.
- A dry vermiculite cap. A dry top layer sits above the hydrated substrate as a physical barrier between the exposed lid openings and the nutrient-rich material below. It's low-tech, and it has been keeping contaminants out for decades.
- Liquid worm castings in the substrate. Standard jars use brown rice flour, vermiculite, and water. We add a small amount of liquid worm castings to supply micronutrients plain BRF lacks — which supports stronger, more vigorous mycelial growth.
- Pressure-sterilized in-house. Every jar is prepared and sterilized in our own autoclaves at our Illinois facility, then sealed and shipped ready to inoculate. No pressure cooker, no prep, no mixing on your end.
Why PF Tek still beats one big bag. One contaminated all-in-one bag loses the entire grow. One contaminated jar out of twelve loses about 8% of it. We made the full case — the history, the honest pros and cons, and how the method stacks up against bags and monotubs — in PF Tek: The Forgotten Mushroom Cultivation Method.
How to Use BRF Jars
The half-pint jar method is the most beginner-forgiving approach in cultivation, and the workflow is short:
- Inoculate. Peel back the foil, wipe each hole with 70% alcohol, and inject through all four. Four entry points means four colonization fronts. A liquid culture syringe colonizes faster and more reliably than a spore syringe, because the mycelium is already alive and growing.
- Incubate. Hold the jars at 70–80°F and leave them alone. No shaking, no opening. The dry vermiculite cap is doing its job.
- Watch. Clear glass is one of PF Tek's underrated advantages. You can see colonization spreading from each of the four points and spot a stalled or questionable jar early — before it affects anything else.
- Birth the cake. Once a jar is fully colonized, turn the substrate cake out and move it into your fruiting chamber.
- Fruit and harvest. Maintain humidity and fresh air exchange in the chamber.
- Dunk and roll. After a flush, submerge the cake in cold water to rehydrate it, roll it in dry vermiculite, and return it to the chamber. Each cake typically gives three flushes before it's spent.
No flow hood needed. The small jar openings and quick inoculation through the foil are clean enough for a normal home grow with basic sanitation. A laminar flow hood reduces contamination risk further and is worth it if you scale up, but it is not required for these jars.
Don't Have a Kit Yet?
These jars are refills — they don't include a fruiting chamber. If you're starting from scratch, our Classic Jar Grow Kits bundle the jars with everything else you need: the chamber, humidity, heat, and our 8-part video grow guide. The Mega Kit and Ultimate Kit were our first products when we opened in May 2011, and they're still made in-house.
Once you own a kit, you never need to buy another one. Come back here for jars.
Frequently Asked Questions About BRF (PF Tek) Jars
What is a BRF jar?
A BRF jar is a half-pint jar pre-filled with a sterilized brown rice flour and vermiculite substrate, ready to inoculate with a culture syringe. It is the core component of PF Tek — the classic small-jar method developed by Robert McPherson in the early 1990s, which introduced a generation of home growers to cultivation. Ours add liquid worm castings to the substrate, a four-hole foil lid, and a dry vermiculite cap.
Why do your jar lids have four holes?
The four foil-covered holes give you four separate inoculation points spaced around the jar. Growth begins in four locations at once instead of spreading outward from a single center, which means more even colonization, less distance for the mycelium to travel, and easier visual tracking through the glass. Most PF Tek jars on the market have one. We explain the reasoning in PF Tek: The Forgotten Mushroom Cultivation Method.
What is the dry vermiculite layer on top for?
The dry vermiculite cap sits above the hydrated substrate and acts as a physical barrier between the lid openings and the nutrient-rich material below. Contaminants that reach the top of the jar have to get through a dry, low-nutrient layer before they reach anything they can feed on. It's a simple feature that has been part of the method since the beginning, and it still works.
Are these jars already sterilized?
Yes. Every jar is pressure-sterilized in our autoclaves in Illinois and ships sealed and ready to inoculate. You do not need a pressure cooker, and you do not need to mix or prepare anything. Peel the foil, wipe the holes with 70% alcohol, and inject.
How many jars do I need for my grow kit?
It depends on the kit. The Simple Grow Kit Plus takes 6 jars, the Ultimate Kit takes 12, and the Mega Kit takes 18. For a full Mega refill, order one 12-pack plus one 6-pack.
Why do your jars include worm castings?
Standard PF Tek jars contain only brown rice flour, vermiculite, and water. We add a small amount of liquid worm castings to supply micronutrients that plain BRF does not have. The result is stronger, more vigorous mycelium and denser colonization compared to a standard three-ingredient jar. It is a small change that makes a noticeable difference.
Do I need a spore syringe or a liquid culture syringe?
Either will work, but we recommend a liquid culture syringe. Liquid culture contains live, actively growing mycelium, so it colonizes significantly faster and more reliably than spores, which have to germinate first. We do not sell spore syringes — see our 2026 Spore Syringe Buying Guide if you want to source one elsewhere.
Do these jars come with a fruiting chamber?
No. These are refill jars only. You will need a fruiting chamber to birth and fruit the colonized cakes. If you do not already have one, our Classic Jar Grow Kits include the jars, the chamber, humidity and heat control, and full instructions.
What happens if one jar gets contaminated?
Isolate it and discard it — the rest of your jars keep going. This is PF Tek's most underrated advantage. Because each jar is an independent container, one contamination event costs you a fraction of the project instead of all of it. A single all-in-one bag offers no such backup. Do not open a visibly contaminated jar in your growing area.
What temperature should I keep the jars at?
70 to 80°F during colonization. If your grow space runs cold — a basement or garage below 65°F — the Ultimate Kit's water-bath heating system is built for exactly that problem and can hold the chamber well above ambient temperature.
Can I reuse the jars?
The glass jars themselves are reusable if you want to prepare and sterilize your own substrate, but the substrate inside is a consumable — once a cake is spent after its flushes, it is done. Most growers buy refill packs rather than mixing and pressure-cooking their own, since the prep and sterilization are the most time-consuming parts of the method.
How many harvests will one jar produce?
Each colonized cake typically produces three flushes. Between flushes, dunk the cake in cold water to rehydrate it, roll it in dry vermiculite, and return it to the fruiting chamber. Yields decline with each successive flush.
Is PF Tek outdated compared to grow bags and monotubs?
Old, but not obsolete. Monotubs scale better and all-in-one bags require fewer initial steps, but neither replaces what PF Tek does best: low entry cost, clear visibility into colonization, and multiple independent containers so a single mistake doesn't cost you the whole grow. For a first grow, that redundancy matters more than saving a few minutes of inoculation. We laid out the full comparison in PF Tek: The Forgotten Mushroom Cultivation Method.