Nasco Whirl-Pak® Write-On Sterile Sample Bags have a convenient white Write-On Strip that will accept virtually any writing instruments (ballpoint pen, pencil, or felt-tip marker) for easy sample identification. Bags are made of high-quality blended polyethylene. Leakproof closure (whirling or tightly folding the tab over 3 times) prevents impurities from entering the bag and contaminating the sample. Bags are sterilized using ethylene oxide gas at an independent ISO-certified facility. FDA approved. Capacity is measured in fluid ounces. Volume and dimensions are approximate.