Product review (5 stars): Excellent Product
The first thing you will notice is how clean this new part it.  Shiny and smells like fresh rubber.  I am very happy with it - and happy to get rid of the old grimy one.

Overall: this part is the same form, fit and function that I expected.

The item I received was indeed a genuine GE part numbered WC03x10010 from "Pandora's OEM Appliance Parts" and it arrived in two days with the Standard shipping speed that was free.  It was estimated to arrive 5 to 10 days later than it did.

The part I replaced measured 3 & 1/16th".  This new part measures 1 & 1/8th".  It did however fit just fine and snug.  Perhaps the original had shriveled up a bit, I don't know.

The opening of the disposal was difficult to measure, but looks very close to 3 & 1/8th".

The disposal it went in is GE Model GFC320F.