A significant number of mattresses sold in the United States contain open-coil units. These types of innersprings are helically laced using a thin-gauge spiral wire that holds coils together in rows. The unit is finished with an outer rod that keeps it together and offers additional strength to the edge of the bed.
At a quick glance, one may assume these two innersprings are too similar to tell apart. While there are quite a few similarities, there are also some differences that are good to know when deciding which innerspring to place in your mattress and how to sell the benefits of each.
The biggest difference is the shape of the individual coil and how that coil shape impacts the count and feel.
Bonnell innersprings are designed with an hourglass shape and are typically made with heavy gauge wire. The knots at the top and bottom provide stability for a supportive surface. This basic coil design, spacing, and wire usage means Bonnell units are typically one of the most affordable units with coil counts in the 300-400 range.
VertiCoil innersprings are similar in shape to Bonnell, but the top and bottom of each coil are squared off so they can fit together in rows. The squared ends of VertiCoil offer more conformability than Bonnell coils and deliver firm support and durability. Knotted VertiCoil coils will be more stable, while open-end coils offer more bounce. VertiCoil comes in coil counts of more than 500 springs in certain queen units.
While both innersprings are made with tempered wire to hold its shape and provide a durable, consistent sleep surface, only VertiCoil innerspring units feature alternating coils to evenly distribute weight. This also counteracts force to deliver proper support and improved perimeter consistency. VertiCoil has a stronger edge due to its use of border rod as well.
Both Bonnell and VertiCoil open-coil innersprings are made of high-carbon wire from Leggett & Platt’s vertically integrated wire-drawing process and create durable, long-lasting sleep surfaces. However, as you now know, the shape of the coil is different for Bonnell and VertiCoil. This allows manufacturing to create unique products for their lineups.