Sue, thank-you for your reply. I just checked my box of 7% Saline and it is in 4mL vials. I always time my nebulizing time with the saline and after 15-20 mins check the level left inside the cup and it’s always at least 1-2ml left in there. I believe the type of actual nebulizer you use makes a big difference also. I just started using a breath activated nebulizer so therefore there is no waste.