Update: Identifying Your Flexineb E3 Cup Flexineb E3 cups are now identified by cap colour: Grey, Green, or Blue. Important:Older cups all had blue caps, and were identified by a coloured label on the front.π A blue cap on your old cup does NOT mean you need the blue variant. How to choose the correct cup: Grey: The grey E3 cup is the universal E3 cup which is compatible with most liquids used in nebulization. Green: The green E3 cup is suitable for use with thicker liquids which are more difficult to nebulize. Blue: The blue E3 cup is suitable for use with thin liquids and smaller doses. Hint: Not sure which cup to order? Most customers need the Grey (Universal) cup. The Flexineb E3 Cup is the heart of the Flexineb E3. Liquids which are intended to act in the lungs are put into the Flexineb E3 cup and are converted into a fine mist to be inhaled by the horse. It is a consumable part with a lifespan that depends on the liquids and volumes nebulized by the cup and how well the cup is maintained.