Pre-Wired LED 5V to 6 Volt 5mm Clear High Brightness Constant
This is a pack of 5mm diameter LED with 20cm wire leads with a resistor for five to six Volt operation fitted into the leads. Nominal current at 6V is 20mA. The lit pictures are taken using a 6V battery pack comprising four AA cells. One LED will run for about 130 hours on Duracell or similar good quality AA alkaline cells. Ten LEDs will run for more than ten hours on such a battery pack. The violet type will show up day-glo fluorescent items and markers but not special banknote inks.
The batteries and pack shown for demonstration purposes in the video are not included.
If using a power supply it needs to be a regulated type. Nominally 6V train set transformers and old battery chargers providing rectified a.c. at a peak voltage higher than 7V will kill the LEDs. Operation from the 5V rail of computer PSUs or 5V USB VBUS is good, and for one LED a 20mA 5V logic output equally so.