Well 440 was a little too much was making my lungs hurt went to 425 much better. I'm thinking it's something in this Russian flavoring. Not sure what they put in it but I'm using it at only .5% and it is still very well flavored but it is a food flavoring so don't have any idea how they can make it so strong. I'm hoping Quackies is better. Will order plenty more. It's not cheap by the way, the way a lot are but like Gary said it is when you consider you are getting a premium flavor for $12 per 100ml that if you bought it from them premixed would be $65.