As long as you are using freezer bags, both Hefty and Ziplock should be fine. For higher temperature cooking, (i.e: vegetables or chicken thighs ), you might wish to consider using mylar, (polyester), bags, or use a vacuum sealer. Thriftyvac sells reasonable quantities of the quart sized mylar bags at 17 cents per, plus shipping. They are really tough bags and can take high temperatures. www thriftyvac.com (n.b. : I have no connection to Thriftyvac, other than being a customer).