IQAir GCX HEPA Pre-Filter H11 (XL)Quick Overview HEPA Pre Filter for GCX units Non woven glass microfiber HEPA filter Surface area: 7. 5m Efficiency of 99% at 0. 3 m (class H11) Filter Life: 12 months (approx) Filter Number: F1 Art. Number: The GCX HEPA Pre Filter H11 is used for the purpose of controlling coarse and fine particulate matter which provides protection of subsequent filters. The media used, is non woven glass microfiber HEPA filter.