Mallory-Sonalert has introduced six new buzzers to their blue MSR Series.  These models: MSR205NR, MSR205NSR, MSR205NJR, MSR205NJSR, MSR205NPR & MSR205NPSR, are rated 2-5 VDC and offer the loudest sound levels for their size. (The “S” in the part number signifies that the part is sealed and it can be exposed to an aqueos wash operation after being soldered.)  These products are used in applications such as, electronic instruments, meters, medical equipments, monitors, and portable industrial electronics.

Datasheet for MSR205 Series

http://www.mallory-sonalert.com/Articles/TechAppGuides/Loud%20Low%20Voltage%20Buzzers.pdf