Modern spring mattress cores (often called "innersprings") are made up of steel coil springs, generally called "coils". The most significant characteristic of an innerspring mattress is the number of coils (or coil count) in the mattress. The greater this count, the higher the quality of the mattress and its construction. Memory foam and Latex foam can often be found in the surface padding of some of the more expensive and higher quality innerspring mattresses. This extra padding aids comfort.