What's the bottom bit in a drum lampshade called?

[LynetteScavo]

I need new lampshades for the living room - to replace up lighters.

I don't want to see the bulb, so if its a drum shade, it needs to have that bottom bit in.

What should I be Googling?

Or can anyone link me to some nice neutral lampshades?

A diffuser? If you're talking about that disk that sits in the bottom of a drum shade. Some shades come with them, but I think you can buy plain white ones separately too.

Ah it's a diffusser! Thank you!