A single 1000ml bag of sterilised vermiculite, ready to use straight from the pack as a casing layer — no need to weigh out from a larger bulk batch. Supplied in a 3 x 4 x 18 inch bag, pH 7.8.
 
Add to the top of your mycelium cake or bulk tub prior to fruiting. The fine particles hold moisture and create the humid micro-pockets mushrooms need to pin — skip the casing layer and pinning tends to be patchy, with a smaller harvest.