From the Bog Dog team:
OMM flasks are flexible and compress down in volume as you drink. Eliminating water sloshing/bouncing inside and reduces the sucking effort. The durable thermoplastic allows for easy storage on the move.
Durable Thermoplastic
Polyurethane (TPU) construction with extra grip
Flexible / squeezable lets you easily squeeze out gels or liquids
Compresses as you drink, reduces sloshing/bouncing of fluids
Slim and lightweight easy to fill and clean with wide opening
Interchangeable straw bite valve
BPA PVC and Phthalate free
Volume: 500ml
Fabric: TPU (Thermoplastic Polyurethane)
Weight: 29g