The short answer
Owens Corning's TruDefinition Duration STORM is UL 2218 Class 4 with SureNail Technology and a 160 mph wind rating, though that rating applies only when Owens Corning component requirements are met and starter is installed at both the eaves and the rakes. The separate Duration FLEX is SBS-modified and also Class 4, marketed for flexibility and cold-weather crack resistance.
Verified specifications
| Item | What Owens Corning publishes |
|---|---|
| Duration STORM | UL 2218 Class 4, SureNail Technology |
| Wind rating | 160 mph, conditional on OC components and starter at both eaves and rakes |
| Duration FLEX | SBS-modified, UL 2218 Class 4 |
| Algae resistance | Coverage effective 01/01/2024 requires an approved OC hip and ridge product |
| Technology | WeatherGuard with an integrated polymeric backing |
Figures above come from Owens Corning published product and warranty documents. Specifications change, so confirm against the current data sheet for the exact product before you sign a contract.
What this means for a roof here
Impact class earns an insurance credit, and in the Hill Country that credit compounds every year you own the house. What it does not do is make a roof hail proof. Manufacturers generally do not warrant shingles against hail damage, and a 2025 study by the Insurance Institute for Business and Home Safety found impact-resistant shingles performed only slightly better than conventional shingles against cumulative granule loss from repeated small hail. Buy the class for the insurance credit and the margin against large stones, not for immunity.
The other thing worth noticing across every brand on this page is how often the headline rating depends on the system rather than the shingle. Wind ratings and warranty tiers routinely require that manufacturer's starter, underlayment and ridge cap. A shingle installed without its specified components does not carry its advertised performance, and that gap is where cheap bids come from.
