21.5 quart liquid capacity stove-top unit holds 7 quart jars. (Note: because this unit uses a weighted vent pipe instead of a stopcock, pressure in the vessel will need to be kept below 15 psi when sterilizing agar, in order to keep the media from boiling.) Each cooker comes with a rack and an instruction booklet. The 921 Pressure Cooker is an effective media sterilizer for the mushroom cultivator on a budget.