Settings for small diamonds?

[MichelleCarmen]

If someone has a stone under .50 ct does a ring such as the following WF ring have to be custom made? The description says the ring is made to accomodate .50-2., so I take it the head cannot easily be switched out or can it?

http://www.whiteflash.com/Engagement-Rings/Styles/Diamond-Settings/-Petite-Open-Cathedral--Engagement-Ring_1211.htm

(I tried one like this today and the style looks pretty on my hand.)