The Synaptic 2.0 waist pack is highly versatile and ideal for most training runs and races. The versatility comes from access to all compartments without taking the belt off. This pack provides the ability to carry hydration, nutrition, home essentials, and is equipped with Z-pole attachments all while remaining very lightweight when loaded down. Details The original Synaptic was Ultrarunning Magazines&';s Top Pick for stability; the Synaptic 2.0 features the same weight distribution ratio and conical belt shape but with upgraded functionality. This pack comes with an UltraFlask 550 Hybrid Bottle in the holster. This bottle is simple, intuitive, and the construction allows for easy access to remove or holster the bottle on the go allowing for a more regulated hydration schedule. This pack features a mesh zippered pocket and additional quick stash pocket on the side of the holster. The front 4-way stretch mesh pocket has capacity for a large cell phone but remains flat even when fully loaded. Shock cord attachments on the front give you carrying options for Z-poles or layers of clothing you want to carry with you. One size fits most.