Lightweight and compact, the Hydrapak's UltraFlasks™ collapse as you drink. This eliminates sloshing and allows you to pack the empty flask tightly to stow on the go. Perfect for integrating into hydration vests, belts, or handheld systems. Suited for a full range of year round activities and backed by Hydrapak's leakproof warranty. 500ml/17oz

Some great features:
Tailwind Hydrapak-500ml
28mm wide opening
High-glow bite valve auto-seals after each sip and includes a twist locking cap for added security.
Made of ultra durable, abrasion resistant TPU and RF welded seams for superior durability and elasticity
Wide working temperature range (can be frozen)
Safe and reliable 100% BPA and PVC free