The Shape of the Coil Springs How the The Offset Coil is an improvement on the original coil design called the Bonnell Coil. These coils are hourglass shaped; offset coils are more expensive, but conform better to the body. You can find some great coil mattresses at this 4000 spring mattress sale. Pocketed Coils or "Marshall Coils" are coils individually wrapped in fabric pockets.
Separating the springs allows for the same comfort and support as other innersprings with more motion separation