4 Pre Poured Petri Dishes… Perfect for beginners or for those who do not have the time or resources to pour their own dishes. These Petri Dishes contain the same PDYA recipe we use in our dishes. Poured in sterile conditions and vacum sealed to insure contamination free product. Dishes are 100x15mm polystyrene. Mushrooms like a diverse diet so switching between different agar medium is generally thought to be a good idea.