The most common mattress type sold is the innerspring or traditional mattress, where the support portion is made from steel coils coming in different shapes and forms. The overall quality of innerspring and its support is determines by shape of the coil, gauge of the coil (thickness of wire - the lower the number, the thicker the coil) and quantity of coils. All better mattresses nowadays use independently pocketed coils providing even support, better contouring of your body, reduced motion transfer and improved durability.
Independently Pocketed Coil
Marshal Coil or better known as pocketed or wrapped coil system is the newest innerspring system consisting of cylindrical coils wrapped in cloth or plastic pockets. The coil is compressed in pocket, thus providing tension at all times. Each coil is in its own pocket, working independently allowing for better conforming to the body and reducing motion transfer. Since coils are not tight together by wire there is significant decrease in unwanted sounds and squeaking. This type of support system is typically softer, made from higher gauge wire compared to tied or continuous innerspring, but on average uses more coils.
This support system is the latest innovation in spring mattresses. It is essentially a small coil with tighter smaller turns inside of bigger coil with a few larger turns. They both create one coil that is individually wrapped and bears the same benefits as Marshal Coil system. It offers a unique feel, where it reacts it two stages, first activating the bigger coil and later putting the smaller coil in action. The coils are usually bigger, made from lower gauge wire providing superior durability.
Braided Coil Innerspring
This design uses several strands of thinner wire braded together into one coil, multiplying the strength of a single wire. It offers superior support and durability and comes with a steep price, usually offered in ultra high-end products.
Tied Coil Innerspring
This system is made from individual coils that have a square top so they can be easily tied together by a spiral wire from left to right, process called helical lacing. Since the coils are connected they work together at all times providing very firm support but still allowing for good conforming to the body. This kind of design provides extremely good durability but lacks in motion reduction. While the coils are tied together in one row, any movement on one side is transferred to the other side by the connecting wire.
Continuous Coil Innerspring
Continuous Coil system is similar to previous Tied Coil system. Its coils are made from one piece of wire and are tied together not left to right, but from the head to the foot of the mattress. This type of vertical helical lacing provides reduced motion transfer from one to side to another but it creates more pressure on the body.
Bonnell Coil Innerspring
This is the oldest and least expensive system comprising of hourglass shape coils. This design offers the least amount of coils per size because the Bonnell Coil is quite wide on the top, making it the least durable. Limited number of coils causes insufficient support for an adult and also provides very bouncy and shaky feel. It would make a decent temporary mattress but definitely not suitable for long-term solution.
Learn more about coils and innerspring mattresses here