Glad you got a hay probe.   That's the brand I bought about 6-7 years ago.  It's still doing the job.   I do take samples from fields and crawling up big stacks or ladders to get a good sample, so a battery drill is required.  At first I used (which was old to begin with) an 18 volt battery drill and then a 20 volt.   A fully charged battery is required.  However, with really a tight bale, it can get harder to core as deep as I'd like.
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Ronelle and Yoyo
2015 Bend, Or, US