Sea to Summit Ultralight SI Mat

Delta Core-V technology is used to reduce the amount of foam used by 20%, while retaining thermal capacity. Using pressure mapping data to define common body contact areas, Sea To Summit strategically placed varying sized vertical air columns within the foam in order to increase the thermal efficiency to weight ratio. This technology places smaller Delta Cores in high body contact areas such as the hips, shoulders, and feet; and places larger Delta Cores in the hollows of the body. This similar technology can be found on the Sea To Summit UltraLight Mat and the Sea To Summit Comfort Plus Insulated Mat which we reviewed previously.

The multifunction valve is designed to make inflation and deflation easier. This high flow-rate inflation/deflation port features 4 valve settings. The self-inflating setting completely opens the valve in order to inflate the mat as fast as possible (Sea To Summit suggests 5-10 minutes). A fine tune setting allows you to adjust the amount of air in the pad; a one way valve makes top ups easy, and a small button allows micro-deflation adjustments for comfort control.  When flipped around, this valve becomes a one-way deflation port, the valve comes with a cap which can be replaced for sleeping and storage. The valve is quite flat to the pad, with very little protrusion so comfort is maximized.

The surface of the UltraLight SI Mat is a 30D lightweight polyester with an extrusion thermoplastic polyurethane (TPU) laminate. What separates this style of lamination from others is that the extrusion process uses a single layer consisting of a combined substrate which is applied to the surface, as opposed to multiple layers of different materials. What this means for you is that the extrusion laminate is a single material throughout, as opposed to multiple layers bonded together, and therefore cannot delaminate as there are no layers to separate. TPU offers performance at low temperatures, high shear strength and elasticity, and resistance to oil, grease, and abrasion.

The foam used in the mat is made of polyurethane, which is the same material used in memory foam. Polyurethane foam is lightweight and durable, though it is sensitive to moisture. The presence of moisture will speed up degradation of the foam, so the fact that this mattress is self-inflating means that less moisture from exhaled breath will enter the foam, therefore increasing the life of the product. If more air is desired than what is drawn in from self-inflation, a few breaths is certainly not going to ruin the pad and the TPU also features an anti-microbial treatment to prevent any mould or fungal growth inside the pad. For those sticklers, Sea To Summit offer a few lightweight, packable pump accessories for purchase as well. 

Foam Type: Polyurethane
Surface Material: 30D Polyester 

• Delta Core-V technology
• Multi functional, high flow rate valve
• Lightweight 30D polyester
• Extrusion TPU lamination
• Anti slip silicone print
• Polyurethane foam

Not the most compact mat on the market but for a foam mat with this R-value it's pretty small.

The Ultra light SI mat makes for a comfortable place to lie down while managing to avoid being a cumbersome to carry around while car or backcountry camping. It’s very comfortable and the self-inflation saves your breath for those breath taking views that you would likely be encountering while out playing. 

I was skeptical of the whole “self-inflating” concept, as I found that I always myself putting a few breaths into a mat anyways; the Sea to Summit Ultra light SI has swayed me from this bias. When left alone for the manufacture suggested time of 5-10 minutes, I found the mat self inflated well and quite comfortable without any breaths required. If I didn’t feel like waiting the full 10 and the mattress was a little on the thin side, the one way valve setting and a few quick breaths was all that was needed to top things up. One too many breaths? Tap the micro-adjustment button a few times before closing the valve for the night and it’s easy to set your desired comfort level. While the valve isn’t quite as stream line as that on the Exped SyncellMat, it is still quite flat to the pad and hosts more features. 

The foam and Delta Cores give this mattress a great R-Value for is weight and thickness. It’s only 95g heavier than the Sea to Summit UltraLight air mat while increasing R-Value by 1.9.  Compared to the Exped SyncellMat, it’s half the thickness, nearly half the weight, and only 0.3 less R-Value. The anti-bacterial and anti-fungal properties of the foam are a nice perk and, along with the extrusion laminate, give me good expectations for the durability of the product.