Laser Printer Drum Kit

Ok, i have worked an a few Laser printers, but am far away from being an expert at them. I have a HP Clolor Laserjet 4500N that is giving me the message that the Drum Life is low, and it needs a Drum Replacement Kit. Im not worried about installing it, but i am curious to what exactly it is. What is included in a drum kit, what does it do for the drum?
Thanks for any help.

 

From what I've read, and correct me if I'm wrong, its just comparable to an ink cartridge for an inkjet. In other words its just the drum and toner.

 

When I replaced one, I think it was just the drum. I'm not sure if this link is totally accurate for the CLJ 4500N, but it may give you an idea (and probably has more info than you're looking for initially, but we are geeks here )

Oh, and those installation instructions are fun!!

 

The drum is not comparable to an ink kit. The 4500 drum kit doesn't come bundled with the toner as some of the other HP models do.

The drum is a light sensitive device. It is what the image is originally created on before it is transfered to the paper. The light sensitive media breaks down over time and exposure to light. This is why it occaisionally needs to be replaced.