It seems like you're referring to a "Di OPC Drum 28A," which is typically associated with the OPC drum used in laser printers and photocopiers. The 28A might be a specific model number of an OPC drum or a toner cartridge, commonly seen in laser printers by brands such as HP, Canon, or others.

Here's a brief explanation of what it likely refers to:

1. OPC Drum (Organic Photoconductor Drum): This is a key component in laser printers and copiers. It is a light-sensitive drum that transfers toner onto paper during the printing process. It is sensitive to light and forms the image or text on paper by attracting toner to the areas exposed to laser light.

2. 28A: The "28A" is often used to refer to a specific model of a toner cartridge or drum, such as HP's HP 28A laser toner cartridge (which is compatible with various HP printers). If it's a specific drum, then it would be part of the printing mechanism for certain printers.

Could you clarify if you're asking about a toner cartridge, an OPC drum, or some specific model related to printers or copiers? I'd be happy to help further if you have more details!