Sea to Summit Ultra-Sil Pack Cover
Sea to Summit Ultra-Sil Pack Cover
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The Sea to Summit Ultra-Sil Pack Cover is a rain cover for backpacks from 15 to 95 liters, made from 30D siliconized CORDURA nylon with no-seam construction and a hydrostatic head greater than 2000mm. Four sizes cover daypacks through large expedition packs, and the cover packs into an attached stuff sack so it is always with the pack when the weather turns. The medium size weighs 113g.
Waterproof Where It Counts
Most backpacks allow water in through seams and zippers during sustained rain, even packs marketed as water-resistant. The Ultra-Sil Pack Cover addresses this directly: the 30D Ultra-Sil fabric carries a hydrostatic head greater than 2000mm, and the cover is built without seam construction, eliminating the stitched channels that let water wick through on conventional covers. A Non-PFC DWR finish on the outer face sheds light rain before it can saturate the fabric. The result is meaningful protection for the gear inside during trail conditions ranging from drizzle to downpour.
Light Enough to Always Carry
At 57g for the XS and 113g for the medium, the Ultra-Sil Pack Cover adds negligible weight to any load. The cover stores in its own Ultra-Sil stuff sack, which stays permanently attached to the cover so neither piece can be left behind at camp or in a car. Because the stuff sack does not detach, the cover deploys and stows in seconds without searching through a pack lid or hip-belt pocket.
Stays Put in Moving Weather
Sizes Small through Large include a keeper strap that cinches the cover tight across the pack harness, preventing the cover from lifting or shifting in wind-driven rain. A drainage hole on the base of the cover lets any water that does collect escape rather than pool. These two details matter most on exposed ridgelines and in sustained wind where a loose cover becomes useless quickly.
Features
- 30D Ultra-Sil CORDURA nylon: siliconized fabric with Non-PFC DWR outer finish and polyurethane inner coating, hydrostatic head greater than 2000mm
- No-seam construction: eliminates the primary water-entry path on conventional pack covers
- Attached stuff sack: Ultra-Sil stuff sack stays connected to the cover so it cannot be separated
- Keeper strap (S, M, L): cinches the cover across the pack harness to prevent lifting in wind
- Drainage hole: base opening lets collected water escape
- Four sizes: fits packs from 15L daypacks to 95L expedition packs
Specifications
| Size | Pack Volume Fit | Weight | Cover Dimensions (open) |
|---|---|---|---|
| XS | 15–30L | 57g / 2.0 oz | 20 × 32 × 45 cm / 7.9 × 12.6 × 17.7 in |
| S | 30–50L | 85g / 3.0 oz | 22 × 35 × 58 cm / 8.7 × 13.8 × 22.8 in |
| M | 50–70L | 113g / 4.0 oz | 28 × 35 × 65 cm / 11.0 × 13.8 × 25.6 in |
| L | 70–95L | 130g / 4.6 oz | 30 × 40 × 70 cm / 11.8 × 15.7 × 27.6 in |
| Material: 100% Nylon (30D Ultra-Sil siliconized CORDURA), Non-PFC DWR outer, polyurethane inner coating | |||
| Colors available: Lime, Blue | |||
| Keeper strap: included on S, M, and L; not included on XS | |||
Who This Is For and Isn't
The Ultra-Sil Pack Cover suits backpackers, thru-hikers, and overlanders who carry a pack in variable or wet weather and want rain protection that weighs under 130g and is always accessible. The four sizes cover packs from a 15L daypack to a 95L expedition pack; anyone carrying gear strapped externally to the pack should size up one size from the pack's stated volume.
The XS size does not include a keeper strap, so it relies on the elasticated hem alone to stay in place. The cover does not seal the gap between the pack harness and the wearer's back, meaning wind-driven rain can still reach the pack through that opening. The cover is sized for the pack body and does not extend over trekking poles, ice axes, or other gear mounted on the exterior unless the buyer selects a larger size.
Common Questions
Don't most backpacks keep rain out on their own?
Most backpacks are not waterproof. Water enters through stitched seams and zippers during sustained rain, even on packs described as water-resistant. The Ultra-Sil Pack Cover's no-seam construction and greater-than-2000mm hydrostatic head address both of those entry points, protecting the pack's contents where the pack fabric itself cannot.
Will the pack cover make the pack completely waterproof?
In most trail conditions, the Ultra-Sil Pack Cover provides adequate protection. Wind-driven rain can still enter through the gap between the wearer's back and the pack harness, which the cover does not seal. The keeper strap on sizes S through L reduces movement and limits that exposure, but the cover is not a sealed system.
How do I choose the right size?
Match the cover size to the pack's stated liter volume: XS for 15–30L, S for 30–50L, M for 50–70L, and L for 70–95L. If gear is strapped to the outside of the pack (sleeping pad, tent poles, wet gear), sizing up one size gives the cover enough material to reach over that external load.
Does the XS size include a keeper strap?
No. The keeper strap that cinches the Ultra-Sil Pack Cover across the pack harness is included on the Small, Medium, and Large sizes only. The XS relies on its elasticated hem to stay in place and is best suited to lighter daypacks carried in moderate rather than sustained wind-driven rain.
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