how come my original brother ink cartridge is different from what I just bought? The model is DCP-130C?

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the model of the printer is DCP-130C
somebody told me that it may be just a compatible cartridge. it is similar in size and shape but the two round openings on one side are different.
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If it just looks different its probally just a compatible cartridge, alot of replacements are.
Your Ink carg. shoud be.
LC 51 Black $2.99
LC 51 Cyan $2.99
LC 51 Magenta $2.99
LC 51 Yellow $2.99
Here is where you can get this ink for this price
Bulk Inkjet Cart.com
If the cartridge you just bought doesn’t have the brother logo or trade mark on it or on the box, it is not an original brother cartridge.