I was sceptical about this product. I didn't install them for about 18 months after I heard about them. I must have put $300 worth of mole bate in my 3 acre yard last year. At the end of the year the mole problem was worse, not better.
As soon as the Wisconsin snow melted, I install these in my back yard where the moles had done massive damage. In only a couple of months I am seeing almost no new mole damage.
I failed to put markers around my devices. OOOPS! I thought my mark I eyeballs would see and avoid while mowing. Well, that didn't work. I just did a survey and I damage about half of them by running over them with a fairly big riding mower. To my amazement. I only found 2 that were NOT still working. Some of them were barely recognizable, but they were still beeping along. You almost have to actually break the solar cell to shut these thing up!
I highly recommend this device. Definely use a small auger to install them and put up a stake or a flag so you can see them in tall grass.

These units do a great and reliable job as strong sonic rodent deterents.

A gopher was going after my best apricot tree, tearing up a large swath of earth. I tried to banish it with used cat litter, but it came back. The day I installed the sonic repellents, it left. I kept the spikes in the ground for a few weeks just to make sure. The gopher didn't return, but a new one did. The repellents drove the new one off in two days. I removed the spikes and thought I was done. But a few days later, I saw fresh mounds in a different part of the same plot. So I reinstalled them. I think our neighborhood infestation is so bad that I'll have to leave these repellents in place indefinitely. I feel very lucky to have found them and hope they last a very long while.

Makes a lot of noise.

Makes a loud beep.