What size candle for this nickel hurricane lamp?

So the candle I've put in there for the photo is obviously too small. What do you think would be the optimal candle width and height for this hurricane lamp?

The glass part is 18cm in diameter and 31cm tall.

I recently bought a couple of these from Freedom and am planning on placing them on the white buffet that we ordered in early January. It was meant to arrive late last month ... fingers crossed it arrives soon :)

B