Microfiber refers to synthetic fibers that measure less than one denier. The most common types of microfibers are made from polyester, nylon, or a conjugation of polyester and nylon. Microfiber grabs dirt and dust and won't let go unless put under running water. Microfiber mops may be washed hundreds of times without a hitch. They may cost a bit more up front, but outlast standard mop heads (both dust mops and wet mops) many times over. This means HUGE savings!