for moisture testing i use a probe from john deere. I would suggest getting the one with a cord from the probe to the tester. They make some with the probe and tester all in one but if you break the probe you got to buy a whole new tester not just a probe. If it is for sampling, i got about 2.5 ft metal probe with teeth on one end and then you take it off and the hay falls out. If your bales are tight a cordless drill wont last long. I use a portable air compressor and put it on an airdrill.