— polyurethane foam (PUF) is a porous synthetic material that is generally more rigid than latex. There are many varieties of PPU on the market, including and materials with memory effect; therefore, the quality and features of this material, usually, depend on the price category of the mattress. Polyurethane foam, unlike latex, is poorly suited for soft mattresses, but it is cheaper and has better hypoallergenic properties (however, latex is also generally considered hypoallergenic).
