Play it safe when shipping radioactive materials with Labelmaster radioactive material excepted package labels. These have room for you to fill in your UN number and read "this package contains radioactive material, excepted package and is in all respects in compliance with the applicable international and National governmental regulations." printed on paper, these air labels have outstanding chemical and abrasion resistance, feature strong adhesion, and help keep you in regulatory compliance. They measure 4 3/8 x 3 1/4 in.