Plastic twist ties are a must have when securely sealing ice bags that are ready for sale. Selecting the right length of twist tie is crucial as well. Too short of a twist tie and the bag will not properly seal. Too large of a twist tie and money is being overspent.
The larger plastic ice bags especially the 50 pound are made from a thicker plastic film. This allows them to withstand the weight of ice in the bag and the weight on top if the bags are stacked. As opposed to the smaller bags which only need to withstand minimal abuse. The nature of the plastic film being thicker makes the "neck" of the bag where the film is gathered much thicker, and more challenging to be securely closed than the lighter weight bags.