The Ultimate Guide to Mattress Coils: Types, Tech & Brand Specs

Ben's Take

The Truth About Inner Springs

Look, the industry loves to hype up "new technology," but sometimes physics wins. The first coil patent hit in 1865, and frankly, the concept hasn't changed much because it works. While memory foam gets the marketing buzz, I see customers at our Encinitas Blvd showroom every day whose bodies essentially reject foam. They need the pushback, the airflow, and the bounce of a coil.

If you're tracking your sleep like I do—keeping an eye on heart rate variability (HRV) and recovery—you know that heat retention and "fighting" your mattress to roll over can wreck your numbers. Coils fix that. But not all springs are created equal. Let’s cut through the noise.

The Hybrid Revolution

A decade ago, reports showed maybe 27% of people slept on pure springs. That data is dead. Today, if you include Hybrids (coils + foam), that number is massive. Hybrids are the sweet spot—they are compatible with adjustable bases, can be compressed for our white glove delivery, and offer the pressure relief of foam without the "quicksand" feeling.

The 4 Major Coil Systems

1. Marshall (Pocketed) Coils

The Modern Standard. Also known as encased coils. These are thin-gauge, barrel-shaped springs individually wrapped in fabric pockets. Because they aren't wired together, they move independently.

Why I like them: If your partner tosses and turns, these stop the motion transfer dead in its tracks. This is the engine inside 90% of the "bed-in-a-box" hybrids we review because they compress easily without breaking.

2. Bonnell Coils

The "Old School." Adapted from 19th-century buggy seats. These are hourglass-shaped steel wires knotted and laced together with cross-wire helicals.

The Verdict: They are cheap and durable, often found in budget dorm mattresses. But honestly? They transfer a lot of motion. If you want a refined sleep experience, look elsewhere.

3. Offset Coils

The Conformist. Similar to the Bonnell hourglass shape, but the top and bottom convolutions are flattened and hinged.

The Verdict: That hinging action allows the coil to conform to your body shape better than a standard Bonnell. A solid mid-tier option, often found in traditional luxury brands.

4. Continuous Coils

The Workhorse. Rows of coils formed from a single piece of wire (like Leggett & Platt's "Mira-coil").

The Verdict: Extremely durable because the load is distributed across the entire wire, but they can feel stiff. You don't see these as often in the modern "luxury hybrid" space.

Nested vs. Pocketed Coils: What's the Difference?

When you're shopping the floor, you might hear sales reps throwing around terms like "Nested" or "Pocketed." Here is the straight talk on what those actually mean for your back.

Nested (Interconnected) Coils

Often referred to in the industry as "Bonnell" or traditional innersprings. These are the hourglass-shaped coils that are wired together.

Feel: Bouncy and reactive.
Cost: Generally less expensive.
Downside: High motion transfer. If your partner moves, you move.
Best For: Guest beds, kids' rooms, or sleepers who love a traditional "hotel bed" bounce.

Pocketed (Encased) Coils

The advanced tech. Each coil is wrapped in its own fabric sleeve (pocket), allowing it to compress independently of its neighbor.

Feel: Contouring and supportive.
Cost: Higher end, found in premium hybrids.
Upside: Zero motion transfer and targeted pressure relief.
Best For: Couples, side sleepers, and anyone dealing with back pain.

The Luxury Option: Coil-on-Coil Systems

You’ll see this construction in high-end mattresses like the Stearns & Foster Reserve or specific luxury hybrids. It’s exactly what it sounds like: two stacks of springs working in tandem.

The Base Layer (The Foundation)
Typically a "Bonnell" or "Offset" pattern of heavy-duty, thick-gauge steel. This layer does the heavy lifting, distributing your body weight evenly and preventing the mattress from sagging over time. It’s the chassis of the car.

The Comfort Layer (The Suspension)
A layer of smaller, flexible, individually wrapped coils sitting on top. These micro-coils conform to your hips and shoulders to reduce pressure points. Because they are independent, they handle the fine-tuning of your comfort.

My Verdict: Coil-on-coil is fantastic for durability and airflow, but it adds weight and cost. If you want a mattress that feels substantial and will last 10+ years, this is a construction worth paying for.