Material:PP-R aluminum Size(mm):20*2.3-110*12. ... layer of aluminum, the expansion co-efficient a samll metal pipe with considerable strength, toughness, impact resistance.4. Corrosion-resisitant ... : thermal conductivity of metal pipes1/200 only, hot water pipe insulation for excellent energy saving effect.7. Light weight, ... , soft color, and beautiful graphics. Aluminum-plastic PP-R composite pipe series