Zerk 40 UL Backpack

A perfect marriage of Mountainsmith's Function-First-Design and an ultralight ethos, the all new ZERK 40! The ZERK 40L, the original cornerstone of our ZERK UL Series, has been tested & developed thru 10's of thousands of thru-hiking miles and co-designed with The Real Hiking Viking (AKA Jabba). When the goal is to hike faster, longer and with more efficiency, consider this award winning pack on your next ultralight adventure.  For this new addition to the Zerk UL series, we've added Zerk accessory compatibility with our Zerk 3L Loki Lumbar and Zerk 7L Toplid enabling you to add 10 additional liters for a robust and modular 50L pack. We've also included modular compressions straps (x4) and field serviceable bungees; not only increasing your versatility on the trail, but also allowing you to strip the weight when minimalism is key.  Additional upgrades for 2026: Materials upgraded to Robic® Nylon X-Grid Extreema (UHMWPE) Ripstop with UTS coating for both the 210d fabric (bottom pan