18 wafers. These expanding potting wafers are equivalent to 15 pounds of potting soil, all contained in a portable storage tube! These 2 1/2" wafers will expand 18 times their volume when mixed with water. This is a new formulation we've added, not only of the water-absorbing benefits of coconut coir, but with the addition of worm castings, kelp, soybean meal, cottonseed meal taking the guess work out of fertilizing for the season. Not only do these wafers promote healthy plants with less work they promote a stronger root system and reduce watering up to 50%. Great for containers and for portability.