Poly bagging refers to the use of clear plastic bags around mail, newspapers, magazines, etc. used to protect the contents from damage as a result of mail handing. In addition, your mail piece can be seen through the protective packaging an added value feature. This is an attractive alternative to using envelopes as it saves the cost of printing the envelope and inserting. Similar to heat sealed plastic wrap, the poly material is available in different thicknesses and automated equipment can accommodate many different sizes.

Source: www.jsmccarthy.com