1 piece- 21mm Double Flared ear gauge (21mm where the lobe sits, flaring is >21mm)
I have only used plastic and stainless steel personally. Plastic stays fairly clean but fades after a few months, stainless steel is only used during the day (dress earrings, of course).
Make sure to buy quantity of 2 for a pair!
Can customize to fit different sizes. Smaller than 21mm may not work out so well with the detail.