Review on Pack of 9 UCEC MB102 3.3V/5V Power Supply Module for Arduino Nano Solderless Breadboard - Enhanced SEO by Jason Cox

Some reviews say these outputs are 12 volts, I've tested each with my Fluke meter that is not breadboard mounted. The first two tested well, 3.27 and 4.99 volts at the breadboard pins. With the jumpers set to 5 volts, I checked the top pins of the power button on the third board and oops! I accidentally closed the 5 volt contacts and the output immediately became +12 volts. Until I know why The next board passed the test normally and the last board I intentionally shorted out and it got back to +12 volts. So these are good power supplies, but they don't have short circuit protection.