AgraTronix HT-PRO [07120] Portable Hay Moisture Meter with 20" Probe, 8-45% Moisture. After the baling process, hay is stacked and awaits sale. Testing at this stage is vital for the same reasons that stood prior to the baling process. With a hand-held electronic probe tester, such as the AgraTronix HT-PRO or DHT-1, you are able to simply insert the probe into the bale and determine its moisture level. Probes come in a variety of lengths, 18”, 20”, 24”, and 32”, giving you flexibility along with reliability.