Use a separate hand syringe to draw up medication. Using a 2″ or longer needle, slowly inject medication into the Aero Syringe. (Needle must reach all the way into the barrel cavity to prevent leaking.) Place the needle cap onto the end of the Aero Syringe needle, taking care not to puncture cap. Leave needle cap in place when you load the Aero Syringe into your gun. When the CO2 gun is fired, the Aero Syringe is pressurized as it leaves the barrel of the gun. (Do not manually pressurize the Aero Syringe.) As Aero Syringe makes impact with animal, the needle cap is punctured and remains on the needle shaft. Medication is dispensed into animal in approximately 2 seconds.