Flashers automatically support all colors of 20ma LEDs with no additional resistors required. Colors can be mixed on the same circuit. Will drive multiple LEDs in series depending on power supply voltage. Resistors can be added to on-board solder pads for LED brghtness control. Input: 7-16V DC Less than 1′ square. LEDs sold separately. Alternately flashes a pair of LEDs (or up to 4 pair depending on power source). Adjustable flash rate from 30 times per second to once every three seconds. On time and off time are equal (50% duty cycle).WARNING: This product can expose you to chemicals including LEAD, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov