Therm-a-Rest MondoKing 3D vs Sea to Summit Comfort Deluxe Self Inflating
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In short: The Therm-a-Rest MondoKing 3D costs $5 less; the Sea to Summit Comfort Deluxe Self Inflating is warmer by 0.7 points of R-value; the Sea to Summit Comfort Deluxe Self Inflating saves 3.2 oz; the Therm-a-Rest MondoKing 3D is 4.25 inches thick against 4.
| Spec | Therm-a-Rest MondoKing 3D | Sea to Summit Comfort Deluxe Self Inflating |
|---|---|---|
| Approx. price | ~$260 | ~$265 |
| R-value | R 7 | R 7.7 |
| Season band | Winter | Winter |
| R-value standard | ASTM F3340 | ASTM F3340 |
| Weight | 4 lb 6 oz | 4 lb 2.8 oz |
| R per ounce | 0.10 R/oz | 0.12 R/oz |
| Thickness | 4.25 in | 4 in |
| Pad type | camping mattress | camping mattress |
| Inflation | self-inflating | pump sack |
| Dimensions | 77 × 25 in | 72 × 25 in |
| Packed size | 26 × 10.3 in | 28 × 7 in |
| Insulation | StrataCore layered open-cell urethane foam | Cross-core open-cell foam under an Air Frame structure |
| Top fabric | 50D | not published |
Shaded cells mark the row where one has a measurable advantage. Weight, thickness, girth and shape are left unshaded on purpose: heavier is sometimes tougher, wider is sometimes warmer, and calling a winner on those would be an opinion dressed as a measurement.
What each one does well, and costs you
Therm-a-Rest MondoKing 3D
- 4.25 inches of real foam is closer to a guest-room mattress than to a camping pad, and it holds that loft all night.
- R-value 7 is a winter number — this works on a frozen campground or an uninsulated cabin floor.
- Self-inflates almost completely on its own given ten minutes; the pump/stuff sack tops it off.
- 25 inches wide in the Large and 30 in the XXLarge, so you can actually roll over.
- Fabric and foam are heavy-duty enough that this is a decade-scale purchase rather than a season one.
- Four and a half pounds and a 26-inch roll — this never leaves the vehicle.
- Getting it small enough to fit its own sack takes a knee and some determination.
- $260 is a lot for a camping pad, though it is priced against a decade of use rather than a season.
- The foam core needs to be stored unrolled with the valve open, which takes closet space most people don't plan for.
Sea to Summit Comfort Deluxe Self Inflating
- R-value 7.7 is winter-capable and the second-highest in this catalogue after the Tensor Extreme.
- Four inches of foam with an internal Air Frame, which is what keeps it stable rather than bouncy.
- A true 52-inch Double that doesn't leave a ridge between two sleepers.
- Stretch-knit face is quiet and takes bedding, so it can be made up like a bed.
- The Airstream HV pump sack and XPEL valve make a mattress this size manageable to inflate and empty.
- Over four pounds in the smallest size and nearly nine in the Double.
- Packs to 28 × 7 inches — it is a duffel-sized object in the boot.
- $265 to $415 depending on size.
- Four inches of foam needs to be stored unrolled with the valve open or it takes a set.