Avery WeatherProof Mailing Labels with TrueBlock Technology for Laser Printers 3-1/3" x 4", Box of 300 (5524) Durable polyester labels provide strong protection against harsh elements TrueBlock technology completely covers everything underneath, so you can reuse boxes, mailing tubes, envelopes and more Customize with free templates and designs at avery.com/print Optimized with laser printers