What is a doughnt key or high E facilitator?

what is the difference between that and a split e mech?

How does the doughnut key work?

One of my flutes needs a repad soon and i wanna know if i should get that doughnut thingy...

It isn't a key, it's an insert! It is an alternative to a Split-e mech. Basically, it's an insert (often doughnut shaped) that goes in the lower G tone hole (the one behind the G# key that closes automatically) to vent air, like a split e! It's sometimes preferred to a Split E mech, as it does it's job, and is a much cheaper alternative. Apparently, a split E produces a stuffy quality that a doughnut doesn't as well.
Plus, people always think you're over venting with a split E, and under venting without one! So it's a nice compromise.
Hope that helps!
Pyface

So is it like something that goes on the pad? or a different kind of pad?

and how much would one cost about?

It's installed in the tone hole. It does not attach to the pad or key. Here's an illustration:

http://www.flutesmith.com/flute-options/high-e-facilitator.html

Prices can vary between shops, but probably somewhere in the neighborhood of $100, perhaps a bit more or less...

OOOH Ok
Thank you