Great for if you want to reflow your own LEDs or for other soldering projects. The 63/37 composition is not verified, but it does seem to reflow well. It is probably not as easy to use as some of the more expensive (Kester, etc.) solder pastes on the market, but it works well and is a great value.
This product contains lead and should be kept out of the reach of children. Care should be taken to wash hands after use.
For best shelf life, keep sealed and refrigerated.