The HeatLink® High Performance Polymer (HPP) fitting system is produced from a specific blend of engineered high performance polyphenylsulfone (PPSU) resins. When combined, these resins offer outstanding long-term performance and chemical resistance. The sulfone family of resins began to replace brass in the plumbing industry over 20 years ago and in the course of time have exceeded the stringent demands of the potable and heating industries.