These are AMAZAZING! They seal great using a BIC lighter. Just make sure to move the lighter back and forth never lingering in one spot for more than a second (Pretty much the same as when you're sealing any shrink tubing). I was surprised to find that the solder ring melts very uniformly every time making it look like an expert solder weld consistently. It only takes about 4 seconds of waving the lighter flame before the solder ring melts so the whole process is much faster than expected.1.) Start by waving the flame back and forth at the middle section until the solder melts. Then, let cool for about 10 seconds.2.) Once the center area is soldered and cooled you can proceed to seal the 2 sides. If you dont wait for the solder to cool in the middle, it will remain pliable, soft, and you'll have to contend with the wire shifting around while you work on sealing the edges.Summary: I bought these as a joke out of curiosity. I was pleasantly surprised and now consider these essential for all future wire projects in low heat areas. I would avoid using them on Motorcycles or in a vehicle engine bay close to the engine block.