Bringing along a collapsible daypack that can be easily packed into your luggage when not in use is a smart investment. After examining numerous packable daypacks with different levels of portability, features, and prices, and testing the top contenders many times, we found that the Sea to Summit Ultra-Sil Travel Day Pack is the best option. When packed, it’s incredibly discreet, almost the size of a keychain accessory. The pack itself is a simple bag made from a super thin, silicone-coated Cordura nylon, which makes it very lightweight and water-resistant. It features reinforced stitching at stress points, enabling it to carry more weight than you might think. However, since the pack is made of such thin, light material, carrying large or awkwardly shaped loads can be somewhat uncomfortable, especially when compared to more structured options.