Your question was: How much air is needed to inflate the Black Stability Trainer?
Our experts said: Your Black Stability Trainer comes filled enough air to get you started. You can add or remove air from the Black Stability Trainer to increase or decrease it's instability and level of balance challenge. The surface should not 'bottom out' to the floor when you stand on it. In general, the surface should be around parallel with the floor (not too convex or too concave).