Flate Plate Collector Specifications High efficiency selective coated copper absorbers. Sturdy, pure polyester powder-coated collector box. Inner tank made in SS 304 (Food Grade), GI with epoxy coating & Electrical grade copper sheet. Electroplate the black chrome coated improves energy absorption, long service life, enduring high temperature. In case water quality is not good; TDS and PPM is so high, and we prefer copper tank