(15) pieces per case. Know what's happening below the surface! Soil probes are excellent tools to understand the condition of your soil and when it is time to water. Overwatering is the most common reason plants perish, especially in planters without drainage holes. The soil probe not only allows you to check the soil moisture at the root zone level, but can also act as a tool to aerate the roots -- the best way to save an overwatered plant before it is too late.  For more information, see our How To Use A Soil Probe guide. Case of 15 pieces per size.