The Hyperlite Backpack, right now there is not a more durable Ultralite backpack on the market. This is not the least expensive Ultralite backpack you can purchase but it is arguably one of the highest quality backpacks.
Hyperlite Junction Backpack
With its DCH150 material this is one of the most water-resistant and abrasion-resistant backpacks made. Hands down, this is one of the best Ultralite backpacks I have used in my 15,000 miles of backpacking.