Sea to Summit's Ultra-Sil pack covers are made of 30D Diamond Ripstop silicone impregnated Cordura, so its waterproof finish can't peel or wear off over time. Siliconized Cordura is about one third the weight of traditional coated nylon. These super lightweight pack covers come in 4 sizes depending on your pack volume.

XS: fits 15-30L packs
S: fits 30-50L packs
M: fits 50-70L packs
L: fits 70-95L packs