The Exos 46 is the next size down from the
Osprey Exos 58, on which we did a full hands on review. We have used the Exos 46 on a few shorts trips and find it is every bit as awesome as the Exos 58, just smaller. In general, we find the 58 liter size to be much more versatile while the 46 size is better for day trips and going really fast and light on thru hikes. Another reason we prefer the 58 in most applications is that for being 20 for bigger, it is only three ounces heavier. The 46 is $40 less expensive.
For thru hiker (hiking long distances with exceptionally light gear), there are more minimalist options that are even lighter. However, the Exos series is rare in that it still has a lid and a frame for being so light. To get lighter than the Exos, you often have to sacrifice comfort or ease of use.
Check out our complete
Backpacking Backpack Review to see how many of the best packs for multi-day backpacking trips competed against each other.