I haven't bought one for 15 years so I'll be no help. Actually, after using it a few years, I got pretty good at mixing compost materials to achieve nice warm piles that weren't excessively hot, so I hardly use mine anymore.

There seem to be two or more types. The simple cheap one (I paid $15 or $20 about twelve years ago). Eighteen inches long, I think stainless? This is the basic one most folks may have.

There there are longer and more expensive types, maybe more of a lab style.

How long does your compost thermometer need to be? Depends on your bins mostly. Mulitiply 18 times 2 = one good for three feet high, since it goes in the middle most often.

Since piles shrink, sometimes quickly, you want to stick it in from the top rather than the side to avoid bending it.

You might have a better chance in finding one at a nursery or garden store, rather than a WalMart or Lowes.

I still use mine after twelve years. Say you made a new pile two weeks ago and want to know if the core is still hot enough (130F or higher) to put some smelly fish parts inside. If it was only 100F I would dig a hole and bury the fish in the ground.

Mine is a Reotemp. It's been a bit abused but still works great with no problems. I did tie a long piece of red surveyors tape to it to help remind me it is still in the windrow.

Lloyd

Here is a link that might be useful: Reotemp website

Thanks to pt03 for recommending the Riotemp. It's affordable AND made in the USA! (The other USA-made one I found was $90!)

I also have a ReoTemp. It's very solid and looks like it'll last a long time. It's temperature readings jive with a different compost thermometer I also have. I first bought a moisture meter made by ReoTemp and I was so impressed with it's quality (extra heavy duty shaft) that I wanted to try their compost thermometer ...same quality, same heavy duty construction. Read the reviews on Amazon and you'll see why I bought these.