Beeper Alarm Sound Buzzer - 2 Piece Set Small 12mm x 9.5mm Electronic Hardware Part for Warning and Confirmation Easy to use Electronic Beeper Alarm Sound Buzzer - Ready to Solder, Positive Negative Measures 11.8mm diameter and 9.5mm height. Input 5V - 12V - It will be a softer at 3V and very loud at 12V. DIY electronic hardware part - so many uses. Easy to solder. Remove sticker label after soldering. Common uses for these beepers are confirmation or warning. Can also be used to locate lost toy (drone, helicopter, etc) and so much more.