This is solder paste for soldering small SMD components in reflow oven or with hot air soldering station. comes in a small container for prototyping or repairing job. This pack is right amount of solder paste for most of the hobby projects. This paste is replacement of solder wire used in Through hole soldering, some times solder flux is referred as solder paste. This solder paste comes in a special container, when it is sealed, it can survive for 6 months. If you open the container and want to store rest of the paste for future use make sure it is tight and place it in a plastic zipper pouch and place it in the refrigerator.