Sea to Summit Comfort Plus SI (Regular)
Published · Researched 2026-09-21
2026 lineup note — naming trap: This is the Comfort Plus SI — the self-inflating foam mat (R 4.1, 3" thick, Delta Core). It is NOT the Comfort Plus Insulated — the dual-chamber air pad (R 5, 2.5" thick). Different construction, different specs, similar names. Verify "Self-Inflating" / "SI" on the listing.
Version lineage (2023–2026)
- Long-running: Comfort Plus SI. STS's self-inflating line built on Delta Core technology (patent-pending foam coring that removes 40%+ of the foam to cut weight and packed size without sacrificing support).
- 2024–2026: Current generation continues: R 4.1, 3" thick, 30D stretch-knit top, multi-function flip valve, PillowLock. Rectangular and mummy cuts in Regular/Large.
Overview
The self-inflating sweet spot: 3" of Delta-Cored foam that self-inflates like a classic Therm-a-Rest but packs smaller and lighter than old-school SI mats, with an R 4.1 rating that covers everything but deep winter. The 30D stretch-knit top feels soft next-to-skin, the flip-over multi-function valve handles inflation/deflation/fine-tuning, and PillowLock velcro mates with STS Aeros pillows. At 2 lb 1 oz for the Regular it's genuinely backpackable for comfort-prioritized trips — the mat for people who want foam-mat reliability without foam-mat weight.
Key Specs (Regular mummy — the reference size)
| Spec | Detail |
|---|---|
| R-value | 4.1 (warm enough for all but the coldest ground, per STS) |
| Claimed weight | 2 lb 1 oz (936 g) — Regular |
| Dimensions | Regular ~72 × 20 × 3 in; Large 78 × 25 × 3 in (1,300 g / 2 lb 14 oz per EU data — see gap-fill) |
| Thickness | 3 in (8 cm) |
| Packed size | ~8 × 13 in (Regular; varies by source — see gap-fill) |
| Insulation | Delta-Cored PU foam (40%+ of foam removed vs classic SI) |
| Fabrics | 30D stretch-knit polyester top / 30D polyester base with extrusion-laminated TPU |
| Valve | Flip-over multi-function valve |
| Extras | PillowLock patches; silicone anti-slip print on base |
Rectangular cuts available: Regular Rectangular 3 lb 1 oz; Large Rectangular 3 lb 4 oz.
Pricing (observed 2026-09-20)
- MSRP: $189.00 (Regular) — observed at BlackOvis (SKU SEAT0092). Larger/rectangular sizes step up.
- Street price observed 2026-09-20: typically at MSRP; occasional 15–20% sales.
In the Box
- Comfort Plus SI mat
- Stuff sack
- Repair kit
- (No pump sack — it's self-inflating; the valve's fine-tune mode handles firmness)
Warranty
Sea to Summit lifetime guarantee against defects in materials and workmanship. STS's warranty service is consistently praised in owner communities.
Support & Parts
STS sells replacement valves and repair kits; the flip valve is field-serviceable. Support responsiveness is a brand strong point.
Community Verdict
The "I don't trust air pads" pad. Self-inflating mats have a devoted following among guides, scouts, and anyone who's been woken by a midnight baffle pop — and the Comfort Plus SI is the modern standard-bearer: warm (R 4.1), genuinely comfortable (3" with a knit top), and far lighter and smaller-packing than the SI mats of the 2000s. The Delta Core weight savings are real but don't mistake it for UL — 2+ lb is a conscious comfort trade. Owner threads praise the reliability ("it just works, every trip") and the PillowLock integration; the knocks are packed size vs air pads and the slow self-inflation in cold weather (warm the mat up first).
Images
sea-to-summit-comfort-plus-si-1.jpg— red, model printedsea-to-summit-comfort-plus-si-2.jpg— red top-end detailsea-to-summit-comfort-plus-si-3.jpg— rolled packagingsea-to-summit-comfort-plus-si-4.jpg— lime, model printedsea-to-summit-comfort-plus-si-5.jpg— red full matsea-to-summit-comfort-plus-si-6.jpg— valve close-up
See [internal image manifest — not shipped] for dimensions, source URLs, and what each depicts.
Research date: 2026-09-20. Specs per STS via dealer listings (BlackOvis, CampingRocks): R 4.1, 3 in thick, Regular 2 lb 1 oz / 936 g, $189. Packed-size figures vary by source — see gap-fill.
Enrichment addendum (2026-09-20)
Long-term durability & warranty-claim reality
Foam-core SI mats are the reliability kings — no baffles to blow, and the Delta Core foam rebounds for years if stored properly (unrolled, valve open). The 30D fabrics are the wear point versus expedition SI mats; groundsheet discipline matters. STS's TPU lamination has a good delamination record. The lifetime guarantee is the backstop, and STS's claim handling is well-regarded. These mats routinely outlast two or three air pads.
Version history — year by year
- 2023 and earlier: Comfort Plus SI established as STS's mid-weight SI line (R 4.1, Delta Core).
- 2024–2026: Current generation continues; the dual-chamber Comfort Plus Insulated air pad (R 5) continues as a separate product — the naming confusion persists, hence the header warning.
Head-to-head vs closest rivals
- vs Therm-a-Rest Z Lite Sol ((/library/gear/sleep-systems/thermarest-z-lite-sol/)): the foam-mat philosophical split — Z Lite (R 2.0, 14 oz, $60, indestructible, uncomfortable) vs Comfort Plus SI (R 4.1, 33 oz, $189, self-inflating, genuinely comfortable). Different answers to "I want reliability."
- vs Therm-a-Rest NeoAir XLite NXT ((/library/gear/sleep-systems/thermarest-neoair-xlite-nxt/)): the weight-vs-reliability duel — XLite (R 4.5, 13 oz) is 20 oz lighter with slightly more warmth; the SI mat wins on puncture-proofing and self-inflation. Guides and youth leaders pick the STS.
- vs NEMO Tensor All-Season ((/library/gear/sleep-systems/nemo-tensor-all-season/)): Tensor (R 5.4, 14.1 oz, ~$200–220) is the performance pick; the Comfort Plus SI is the "it'll never let you down" pick at a similar price. Shoulder-season warmth favors the Tensor.
Care & maintenance
Store FLAT or loosely rolled with the valve OPEN — compressed storage kills SI foam (this is the #1 killer of self-inflating mats). First use: unroll, open the valve, wait 15–30 min, then add a few breaths via the valve for full firmness. In cold weather, unroll the mat inside your tent early — cold foam self-inflates slowly. Clean with mild soap; patch with the included kit.
Buying traps
- Comfort Plus SI vs Comfort Plus Insulated: the critical trap — the Insulated (air pad, dual chamber, R 5, 27.7 oz Regular, $129.99–$199.95) is a different product. Listings and even some retailers mix them up. Check for "Self-Inflating"/"SI" and the 3" thickness.
- Rectangular vs mummy: rectangular cuts weigh ~1 lb more (Reg Rect 3 lb 1 oz vs 2 lb 1 oz) — verify which cut the price covers.
- Packed size variance: sources report 8×13 in (BlackOvis) to 33×15 cm / 13×6 in (EU) — generation and measuring-method variance; expect a largish roll either way.
Community Verdict — additional voices (appended 2026-09-20)
- Guide/scout communities: the default recommendation where reliability beats weight — "it just works, every trip" is the recurring line.
- PillowLock ecosystem: owners pairing it with the STS Aeros pillow cite the integrated system as the best sleep setup they've owned.
- Cold-weather note: self-inflation slows dramatically in the cold — experienced users unroll it first thing at camp, a tip that appears in every SI-mat thread.
Key Specs gap-fill (appended 2026-09-20)
- Standard for warmth: R 4.1 per STS (ASTM F3340 status not explicitly confirmed on the listings retrieved — treat as manufacturer-rated; do not assume ASTM comparability without verification).
- Weight in both units: 936 g / 33 oz / 2 lb 1 oz (Regular, per BlackOvis); Large 1,300 g / 45.9 oz (EU listing — conflicts with BlackOvis's "2 lb 2 oz" Large figure; variance disclosed, not resolved).
- The air-pad sibling: Comfort Plus Insulated (dual-chamber air pad) — R 5, 2.5 in, Regular 27.7 oz / 785 g, $129.99–$199.95 — is NOT this product.