I did some testing on these and find that they did in fact trip more or less as expected within a range. I use these as both an on and off switch and a fuse, sometimes on mission critical stuff I have a regular fuse as well. These act more as a “slo-blo” fuse rather than an instant off circuit breaker inside certain ranges. They will blow instantly but only if you go way up in amperage.First off, remember, these aren’t a fuse, they are a circuit breaker and their tripping or lack there of come down to several factors, including but not limited to:1. Rated current2. Ambient temperature3. Tripping current4. Tipping time5. Tripping rangeAnd more factors than this. With a mild overload within the correct voltage range it can take an hour for these things to heat up and trip. Thus as I mentioned, the “slo-blo” type of thing. There is something called a circuit breaker trip curve and an instantaneous trip amperage. All of this factors in. When rated at 40 amp like these, they don’t instantaneously trip at 41A or whatever. Why? Because what if you have an item you turn on and it pulls 80 amps for a second or two while a motor spins up. You’d be tripping it all the time and calling it a piece of crap.On higher end versions of DC Circuit breakers (Marine, Aerospace etc.) you can actually set the instantaneous trip.Look around and you might be able to find the trip curve for breakers like this and get some idea of how this one will work for you if you’re worried about it.To make good use of these and build in a safety margin, up your wire size by 1 and you’ll be sure not to burn anything. Your wire should always be able to handle way more than your trip setting. So if you need to pull 35 amps constant, and use a 40 amp version of these, remember they could run for hours possibly at 50 amps before they got hot enough to trip, where as, say 150 amps, would trip it instantly.Size wire accordingly.I hope you found this helpful. [...]