The West Coast Trail is notorious for it's wetness. One investment we made prior to the trip last year was a couple of dry bags. These don't show up on my gear-list as I wouldn't normally feel that they are necessary, but they sure gave great peace of mind. They delivered bone-dry down night after night – even after a few mud-pit submersions 🙂
At 0.9 oz for the Small (4L) – I ended up taking two. One to cram in my down sleeping bag and one to protect my spare clothes. Theresa needed to take the Medium (8L) at 2.3 oz to fit her bulkier bag.
Available from backcountrygear.com starting at $11.95 for the small.