Bonnell spring mattress systems are the most traditional type of innerspring mattress. The Bonnell coil has an hour glass shape (wider at the bottom and the top than the middle) and are interconnected with a mesh of metal to make the spring system.

In many traditional innerspring mattresses from the 20th century and still some entry level models today have used the Bonnell spring to create durable and supportive mattresses.

Though this system is good at providing even support, there are complaints of aggravated pressure points and discomfort with Bonnel spring systems.

Pros: Durable materials and traditional even feel.
Cons: Pressure point discomfort and motion transfer issues.