Once polymers are used reliably in a specific service, they become the material of choice due to their cost effectiveness. However, to choose and apply polymers dependably, one must consider their unique properties – they are different from the metals we use industrially. Through various examples of damaged and failed parts, this paper illustrates fundamental information about choosing, using, and keeping polymers in service. Polymers are subject to permeation, oxidation, aging, fatigue, installation damage, and other damage.