"Why are there so many ID card printer ribbon types? And how do I choose which one is right for my 
printer?"
Those are two questions that I frequently get asked about! The bottom line is that our printer manufacturers make different ribbons for a variety of different functions.
"But what's with all the letters for each of the ribbons?"
Well, unlike standard paper printers with their ink cartridges, ID card printer ribbons use primary colors – combined with heat – to print all the colors onto the card. Each letter you see in a particular ribbon type represents a color or type of ribbon.
To start things off, the primary colors are listed as letters: "Y," "M," & "C:"
Y = Yellow
M = Magenta (think of the color red)
C = Cyan (think of the color blue)
Then you can have two other letters floating around in the ribbon's acronym:
K = Black
O = Overlay
Now how to choose the various ribbon types:
YMC – This ribbon type is recommended for laminating or retransfer printers only. Having no "O" panel will cause your cards to look wet, and the color will start to smear very easily. It's also advised that if you need to add black text and/or barcodes to your cards that you use a different ribbon.
YMCK – This ribbon is also recommended for laminating or retransfer printer only. Remember: you want that "O" panel to protect of all the color you are laying down or applying to your card's surface. The added "K" gives you a resin black which produces a crisp, sharp black color for barcodes and text.
YMCKO – This ribbon is by far the most popular ribbon. It can lay down any color you need, just like YMC ribbons. It has the added black ("K" panel) for text and barcoding and also has the "O" overlay panel to protect your card.
YMCKOK – Notice the two "K" panels? Why on earth would they do that? It's actually simple. A majority of organizations will lay all their color down on the front side of the card – including the true black – and then print only black text and/or barcodes on the back. This helps to alleviate the cost of using color on both sides. Pretty smart, right?!
YMCKK – Here's the exact same ribbon as the YMCKOK, except that it is missing the "O" (overlay) panel. This is an option for a retransfer or laminating printer only.
YMCKIKI – Now we're adding another letter: "I" which stands for "inhibit." This ribbon is used for retransfer printers only. This is a simple YMCKK two-sided card printer ribbon: color on the front and black only on the back.
Remember, we don’t need the "O" panel with a retransfer printer. The "I" panel prohibits the HDP film from adhering to the surface. Why is that important? Because if you're using contact smart cards, magnetic stripes, or embedded holograms, it will protect those features. Remember, the card printer is using heat to lay all down the color.
YMCKT – Another letter? Yes, another letter! "T," which stands for topcoat. The "T" panel is the exact same thing as an "O" panel. Datacard and Polaroid ID card printer manufacturers are the only brands that use a "T" panel instead of an "O" panel. And yes: they are both clear coats to protect your card.
YMCIKH – Now we come to the most specific ribbon out there. It's made by Fargo for use in their retransfer HPD5000 printer. Did you notice the missing "O?" The "Y," "M," and "C" panels are for printing full-color images. The "I" panel is an inhibitor panel that prevents printing over surface foils, smart chips, or other card features. The "K" panel is black resin and is typically used for printing text and barcodes. The "H" panel is a heat seal panel that helps ensure that the HDP film adheres to cards with uneven surfaces. So what type of card would that be? Typically, it's for customized proximity or smart cards that have pre-printed foil and holographic images on top of the card.