About: Features: An eco-friendly way to carry gels, electrolytes or your own nutrition mix Standard 28mm opening lets you fill easily and holds 5 servings of enegry gels or nutrition Shrinks as you drink to eliminate sloshing and collapses fully to a tiny size when empty Made with ultra-durable, abrasion resistant TPU material and has Hydrapak's Beyound Lifetime Guarantee Can be frozen or filled with hot water (max temp 60'C / 140'F) Safe and reliable, 100% BPA & PVC free Materials: