A single/double automatic heat sealer is a great heat sealer for closing thick bags. The heat sealer has 2 wires, one in the upper jaw and one in the lower jaw. If you are sealing a really thick bag you can turn on both wires to generate enough heat to seal the bag. If you then need to close thinner bags you flip a switch and only one element heats up. This way you do not melt your thinner bags. This automatic impulse heat sealer is very versatile for sealing a spectrum of bags. Because these machines can be purchased in 5mm or 10mm wire you can really tackle a heavy bag.