The UltraFlask is made of soft lightweight material which conforms to pockets and shrinks as you drink to minimize water movement. It can be used with or without the tube and comes with an auto-sealing bite valve cap and an adjustable drink tube cap. It is made of ultra-durable, abrasion resistant material for durability and elasticity and has a large 42mm opening which lets you fill it easily with ice and drink mixes. It is 100% BPA & PVC free and has a wide working temperature range (can be frozen - max temp 60° C / 140° F).