Tried and tested. :) These were specifically designed to use three AG3 batteries - the cheapest batteries I can find on Ebay - and a single 5mm LED. 100 of these batteries is $4 shipped: http://www.ebay.com/itm/Wholesale-100pcs-AG3-LR41-SR41-392-196-Alkaline-Button-Cell-Coin-Battery-/291376606158?pt=LH_DefaultDomain_0&hash=item43d7662bce And 100 LEDs is $1.31 shipped: http://www.ebay.com/itm/Lot-Of-100-Pcs-5mm-Round-Blue-LED-Super-Bright-Bulb-Panel-Board-Lamp-Light-/261752989837?pt=LH_DefaultDomain_0&hash=item3cf1b1a88d Two of these are included, as I generally like to spin two lights at once, instead of just one. I'm still not very good. Battery life at full brightness is more than 8 hours. At just under half brightness, the L.E.D. will still produce light 2 days later. The LED part does need to be drilled (any standard drill set will have a drill that works) - haven't figured out tolerances on it yet. Instructions: Drill the hole to fit a 5mm L.E.D., tape together three AG3 batteries, bend one L.E.D. out straight, put the L.E.D. into the hole in reverse to bend the leads, friction fit the L.E.D. and 3 batteries into the space - this will keep the LED on. Slip some string through the holes, and you have electronic poi!