The arm sealers are the lowest cost method for sealing poly bags with an air and water tight seal. Round wire, 2 mil, 5 mil seals available. Models available from 4" - 40".
To properly use, start at a low setting and keep bumping up the timer until you achieve a good seal. Generally the thinker the poly, the longer the cycle. Make sure the operator keeps the arm down after the machine's red light cycles off for a few seconds. This will insure a better seal after the poly congeals and cools down.