V4L carts come in one of two ways: pre-filled or blank. Pre-filled carts come with e-liquid (juice) already inside them. Blank carts are empty and must be filled with juice before  using.
Blank carts"
Why should I juice? The advantage to  pre-filled carts is that they're ready to go right out of the package. Just take off the rubber tubes (also known as cart  condoms), screw  on a battery and vape. These are perfect for people new to vaping, and for getting the hang of vaping. Filling carts yourself is a great way to save a little cash. Its more cost-effective to buy blank carts and juice than getting the pre-filled ones. Once a vaper has enough experience, has decided on a few favorite flavors, and is interested in learning more, they often venture into the world of juices. "Juicing" in the vaping world refers to the act of an individual filling carts manually.  There are several different methods to filling carts yourself, including using needles and cart condoms! Some work better than others. There is no one particular correct way to do it. Like  many systems in the ecig industry, juicing is a personal preference. V4L's method The manner in which V4L representatives explains the way to juice is simple and easy to learn. V4L's recommendation for juicing follows. You may fill blank carts, or empty carts that came pre-filled. First remove the cart from the battery (if applicable), and take a thumb tack to gently remove the small white disc. Simply stick it in the small hole and pull out  to one side, while the disc comes out of the cart (not hard to do). Place to the side. Hold the cart at a 45 degree angle with the bottom (part that fits  on the battery) facing down. Take a bottle of juice and drip 5 drops into the cart on the inside wall, while turning the cart after each drip. This will ensure an even fill. Then wait for the juice to get soaked into the white filling and drop 5 more (using the same procedure).
Premium Juice"
Continue this process for a total of 20 to 30 drops. Then set the cart on an even surface for about 10 minutes. At this point you need to cover up the top of the cart, with the white disc that you set aside earlier. After the 10 minutes are up, the cart is ready to be screwed onto a battery and vaped. If you get juice in your mouth, it means the cart was overfilled. Just remove the cart from the battery, and blow the excess juice through the bottom of the cart onto a paper towel (this is the opposite way in which you filled it). Then you can vape again. Variations on the theme There are two variations to this process. The first  is the 'Taryn spin' - a way to get more liquid into the cart. After filling one with 20 drops, you can put the cart into a lanyard and spin it around and around. The centrifugal force will push the juice into the far ends of the cart, creating room for more. After spinning a few times, remove the cart from the lanyard and add more juice. The second variation to this method is the mouth piece. Instead of using the small white disc, you can use a drip tip. This is an accessory that extends the length of the cart. To use it, simply push the drip tip onto the cart and it will stay firm inside, until you pull off. The purpose of the drip tip is two-fold.
Delrin Drip Tip"
One  reason is the ease of use. If you refill several times a day, you'll want to make the process as easy as possible. Just pulling off the drip tip and pushing back on, is easier than using a thumb tack to remove the white disc. People also use a drip tip because their carts get too hot for their liking. The drip tip provides a barrier between your lips and the cart. It can be used with both pre-filled carts as well as blank carts, and with WOW carts, or CoolCarts. Important note If you decide juicing is for you, V4L highly recommends using manual batteries for carts that you fill yourself. Unlike automatic batts, manuals are completely sealed. If juice happens to leak into an auto, it will most likely ruin the battery. If you already juice, what method do you use? If you haven't tried juicing yet, give it a go. Be sure to let us know how you like it!