These 8-inch by 10-inch vacuum bags from VacMaster (model 30614) are glossy transparent nylon / polyethylene, as are all VacMaster vacuum storage bags. The difference here is that these bags are 4- millimeters thick (standard bags are 3mm) and so are especially puncture-resistant. They're ideal for storage of boney, spiney or sharp-cornered items that might tear through a thinner bag. Package of 1000. Once they're sealed, these bags can be heated in a microwave, cooked in a sous vide bath, or boiled for durations of up to 20 minutes. Specially designed for tight seals in chamber vacuum sealers (and no, these 4-mil bags aren't recommended for use in external or non-chamber suction vacuum sealers. B.P.A.-free, these superb bags are F.D.A. approved & will prevent freezer burn and keep foods fresh for up to 5 times longer than alternative means of storage.