Extremely sensitive and very effective. I鈥檝e caught mice, voles, a shrew without issue. The people saying they put PB and came back to a still set, now empty trap, I鈥檒l bet my life they were raided by ants... I鈥檝e run into that a couple times. Had a small family of voles take up residence in my raised bed garden after construction next door uprooted them from their home. I set the trap outside their exit hole, turned a bucket upside down with a rock on top for safety (didn鈥檛 want to injure any backyard wildlife or my dogs) and had one in the trap every morning, 4 days in a row. When I went 2 straight nights with nothing, I knew I had them all. Never had garden holes again. I had lived here 4 years and never had a mouse in my backyard workshop, but again, once construction began next door I started to see droppings. That鈥檚 when I purchased these and was catching mice daily until suddenly nothing. I had been using those electric traps, which also work, but they have a limited lifespan, are very costly and carry the added cost of batteries, lots of batteries. I switched to these and never looked back. When I unboxed them I thought they were cheap garbage, but they鈥檙e better than you think. If you鈥檙e struggling to set them then you鈥檝e put too much PB and it鈥檚 weighing down the trip pedal, that鈥檚 how sensitive they are. I don鈥檛 remove the cup from the bottom; not keen on handling them after there鈥檚 been dead rodents in there. I just use a chopstick from sushi take-out to get just enough bait in the middle of the cup; pinch and hold the jaws open for safety, then use a stick to slide it in place. Easy to set, empty, bait and re-use. I love these things!