Pyramidal anechoic absorbers are typically made from a foundation of open-cell polyurethane foam that is volumetrically loaded with carbon and fire retardants. This material is selected for its dielectric properties, which are well-suited for ultra-broadband performance in RF and microwave applications. The foam is shaped into a pyramid or cone shape, which helps to absorb and dissipate incoming RF energy, reducing reflections and improving the accuracy of measurement and testing.