For many people, there’s still no beating a quality inner spring mattress. The first inner spring mattress was patented in 1865. The above picture is from a coil spring patent issued in 1952. Coil systems have really not evolved all that much in the past 75 years. They offer good pressure relief and breathability and nothing can beat their bounce.

According to a 2016 report by the Better Sleep Council, 27% of us are sleeping on spring mattresses. That doesn’t include pillow top mattresses which also may have spring systems. Including that, would bring the number up to 57%. If you add the new breed of hybrids which are spring and foam, that number grows 10% up to 67%.

There are four major types of coil systems in use right now. They are as follows:

• Continuous coils (the Leggett & Platt brand name is “Mira-coil”) is an innerspring configuration in which the rows of coils are formed from a single piece of wire. They work in a hinging effect similar to that of offset coils.
• Bonnell coils are the oldest and most common. First adapted from buggy seat springs of the 19th century, they are still prevalent in mid-priced mattresses. Bonnell springs are a knotted, round-top, hourglass-shaped steel wire coil. When laced together with cross wire helicals, these coils form the simplest innerspring unit, also referred to as a Bonnell unit.
• Offset coils are an hourglass type coil on which portions of the top and bottom convolutions have been flattened. In assembling the innerspring unit, these flat segments of wire are hinged together with helical wires. The hinging effect of the unit is designed to conform to body shape. LFK coils are an unknotted offset coil with a cylindrical or columnar shape.
• Marshall coils, also known as wrapped or encased coils or pocket springs, are thin-gauge, barrel-shaped, knotless coils individually encased in fabric pockets—normally a fabric from man-made, nonwoven fiber. Some manufacturers precompress these coils, which makes the mattress firmer and allows for motion separation between the sides of the bed. As the springs are not wired together, they work more or less independently: the weight on one spring does not affect its neighbours. More than half the consumers who participated in a survey had chosen to buy pocket spring mattresses.

Marshall coils or pocket coils are the post popular among the online brands because they allow the mattress to be roll packed and shipped in a box. They are also compatible with adjustable beds. Most of the online inner spring brands also include foam in their construction. They are often referred to as hybrid mattresses because they have coils and foam. Hybrid mattresses are very appealing to people looking to transition from a traditional spring mattress to more of a memory foam feel.