I have two of these, one with PB2 and one with Shakeology. The compartment is almost filled with a serving of the chocolate Shakeology. Holds 4 servings.
After that I just shake out a couple of tablespoons of PB2.
This and a shaker cup (free if you do certain types of Shakeology orders, ask me how) are what I use on the road for a snack or breakfast.