Some ecigs come ready to use right out of the package. Some ecigs need to be filled with juice before you can use them. The advantages to filling ecigs yourself are that you can mix flavors together and save money. Here are four different cartridges for ecigs, and how to fill them. Cartomizers Cartomizers or "carts"/"cartos" come either prefilled with juice or blank. Often people use these until they run out of juice and then toss them. Others refill them until they start to taste funky. Blank cartomizers come empty without any juice. You have to fill them before using them. To fill/refill a carto, follow these directions: 1. Use a thumb tack to carefully remove the small white disc by sticking the tack into the small hole and pulling out to one side. 2. Hold cart at a 45-degree angle. Drip 5 e-liquid drops into inside wall of cart, rotating cart after each drip for an even fill. Repeat after juice is soaked into white filling. Carts can hold  20  €“ 30 drops. 3. Replace small white disc onto cart and set on an even surface for 10 minutes. Cart is now ready to attach to your battery for vaping. If e-liquid comes out while vaping, the cart was overfilled. Remove cart from battery and blow excess juice through bottom of cart onto a paper towel. Tanks Tanks come in a few different sizes and hold e-liquid in a cartomizer surrounded by an acrylic or glass tube. Because of this, they hold more juice than a carto alone. Another nice feature is that it's easy to see when you need to refill it, since the tank is clear. Tanks always come empty and must be filled with e-liquid before use. To fill a tank: 1. Pull cartomizer through the bottom of the tank 1/2 inch. You should see a small gap between the top of the tank and the clear acrylic side of the tank. 2. Tilt tank slightly and fill directly into the cartomizer until it overflows. Completely fill tank surrounding the cartomizer. 3. After filling, push cartomizer back up inside the tank. Put your drip tip on the cartomizer and get vaping. When the space between the cartomizer and the wall of the tank is dry, it's time to refill the tank. Smileomizers Vapor4Life created the Smileomizer that is like a regular cart on steroids. Smileomizers comes in two sizes - the small holds 3.5ml of juice, and the large holds 6ml. It's mouth piece is soft and chewy, and comes off to reveal white polyfill, like a cartomizer. All Smileomizers come blank and must be filled with juice. You fill and refill Smileomizers similar to regular carts: 1.  Pull off the soft mouth piece and drip 70-90 drops (120-150 for Large) against the side of the cartomizer into the white filler material. Work your way around in a circle, avoiding the center hole. 2. Let sit for 5 minutes. If the polyfill is not saturated, repeat this process. Replace the drip tip and mouth piece, screw onto a battery and you're ready to vape. 3. Once you experience a lack of vapor production or flavor, it is time to refill the Smileomizer. EGO Mega Carts EGO cartos are really big cartomizers (thus the name 'mega'). They hold 5 times as much e-liquid as regular carts. EGO Mega Carts are made specifically for EGO batts, and aren't compatible with any other batteries. EGO Mega Carts come blank and must be filled with juice before using. Follow these instructions on filling: 1. Remove the black tip exposing the white polyfill material. 2. Hold cart at a 45-degree angle. Drip juice into the filling on the inside wall of cart, rotating cart after each drip for an even fill. Repeat after juice is absorbed into white filling. One cart holds 125 drops. 3. Replace black tip and let the cart sit on a flat surface for 10 minutes. No matter what cartridge you use, the most important thing to remember is to always keep it wet. If there's not enough juice to produce vapor, it will burn and taste awful! Another thing to keep in mind is that carts and tanks can be filled many times before needing to be replaced. This saves you a lot of money by reusing them.