Is there ever expansion or shrinkage with ShingleVent II plastic ridge vent?

Here is some information about expansion and shrinkage specific to ShingleVent II plastic ridge vent.

Expansion in plastic can happen.  A temperature of  degrees F in ShingleVent II can result in an overall expansion of 1/8 inch over the 4-foot length of the product. Therefore, we recommend anytime the temperature is below 60 degrees F that a 1/8-inch gap be left between each 4-foot piece of ridge vent during installation. If this gap is not maintained then the ridge vent pieces could expand in hot weather and cause the ridge vent to buckle at the joints creating a wavy appearance. The only time that shrinkage is an issue is if the installation is done during extremely hot weather. In such cases, the installer can reduce the recommended 1/8-inch gap between four-foot sticks of ridge vent.