This is a box to hold a 9 volt conductivity tester. It is designed to comply with the Don't Judge a Powder event for the middle school and high school Science Olympiad competition.You will need to build the conductivity circuit as detailed on this web page http://scioly.org/wiki/index.php/Can't_Judge_A_Powder. Sorry I couldn't get the link to work right, so you'll have to cut and paste it into your browser. You'll want to buy a standard 5mm LED so it will fit in the hole. I put shrink wrap around the connections and the resistor. Print out the box and lid. PLA would probably be best to avoid the cracking sometimes seen in thin walled ABS prints. To assemble the print, push the LED through the hole. You can super glue it if you want. Fold the resistor and excess wire next to the battery as shown in the unassembled picture. Push the battery and wire into the box. Feed the two leads out through the lid holes. Put the lid on the box. You can tape it on if you want to make sure it stays snug. The pictures show the LED lighting on a glass of salt water and not on a glass of filtered water.