Review on 60PCS Heat Shrink Butt Wire Connector Kit - Insulated Waterproof Electrical Marine Automotive Crimp Terminals Splice by Michael Domus

I was able to heat-seal a few of these successfully with a lighter. The results weren't pretty but they did seem to keep wires spliced.Then I discovered the 6.56FT Long Heat Gun . Clever name aside, it is inexpensive, conveniently sized, and doesn't cost much. In particular it's great for these connectors!Anyway, these work with matches or a lighter, sort of. However to get great results get even an inexpensive heat gun.