the seal indicators Seal Check (for clear pouches and tubes made from paper / film) and Seal Check HDPE (for clear pouches and tubes made from uncoated Tyvek® / film) make defective areas visible on the dark indicator strips. hawo Seal Check is not suitable for use with side-fold films. The hawo Seal Check comes in a package designed especially for ease of useand with a reference card for assessing the result