The Force is strong with this keychain! This emits a bright LED light and is approximately 5 inches long. Your choice of colors: Blue (like Obi Wan Kenobi and early Luke Skywalker) Green (like Yoda, Qui-Gon Jinn and Luke Skywalker) Red (like Darth Vader, Darth Maul and Kylo Ren) White (like Ahsoka Tano) Save a bit by buying one of each color (red, blue and green) for $26. For those who want party favors, I also sell them in packs of 10 with a further discount. Most of the lightsabers produce a solid light when turned on. Some blink slow, fast and solid. Each light is tested before shipment and comes with a plastic guard piece to protect it from turning on while shipping. Remove that plastic protective guard (which prevents it accidentally being turned on while shipping) to make it easier to press the button. We record a video of us testing your unit(s) to make sure they operate properly before we ship them to you. Coldness can also affect your unit so if it has been sitting out in your cold mailbox for hours, please allow them time to warm up to room temperature. Also make sure the keychain end is fully screwed tight so the batteries are properly connected to the electronics inside. BATTERY REPLACEMENT: The 3 very small batteries (LR41) are replaceable but it isn't an easy process. When you open it up, that silver button will also fall out and getting it back in that hole will not be fun -- you'll need long narrow tweezers or something along those lines to get it back in the hole so figure out a way to keep the button in the hole before you open it to get out the old batteries. I'd probably use a hot glue gun to put a blob of glue around the button, which later can be easily peeled off once it is back together and cooled off. Or open it so the button is facing down and keep it that way so gravity will keep it in its place (hopefully). You also need to make note of the orientation of each battery so you can put the new ones back in correctly -- carefully and slowly take the two halves apart. A little circuit board will remain attached to the LED portion of the light and at the other end of the circuit board is a black plastic piece that holds at least 2 of the batteries with the third exceeding its height which will, when inserted back into the lightsaber metal handle, touch the metal end completing the circuit.