Get the word out on your shipments with Labelmaster Un3373 labels. Preprinted with biological substance, category b, on the tab, these provide a quick reference for shipping Personnel to help ensure that handling instructions are communicated. Printed on paper, these air labels have outstanding chemical and abrasion resistance, feature strong adhesion to corrugated boxes, and help keep you in regulatory compliance. They measure 4 x 4 3/4 in.