Now in one of the most popular sizes, we have brought a flashing led. The 5mm flashing round top cool / clear white led will automatically start flashing once it is appropriately hooked up to power. There is nothing extra needed when hooking this led up to power. A power source, led, and resistor is all you need. 2hz = 2 cycles per second or about 120 times per minute. It will flash on and off 2 times each approximately per second. We consider this a “fast� flashing LED. The frequency is approximate.We use and have only the highest quality leds out there. 5mm Round Top Cool Clear White Fast Flashing 2Hz LED - Super Bright Size: 5mm Round Top Clear Flashing, Color: Cool / Clear White, Luminosity: 14,000-15,000 mcd Forward Voltage: 3.0-3.4v, Current: 20mA, Wavelength: N/A Cool / Clear White Viewing Angle: 20-30 Degrees, MountStyle: Through Hole (DIP), Lens Color: Clear Super bright LEDs, used for mods, RC, adruino, cars, HO Scale models, planes, trucks, adafruit projects, halloween, christmas, PC, Ultra Light, etc... Manufacturer Lighthouse LEDs Item model number 5MMROUNDTOPFLASHINGLEDCOOLWHITE2HZ