This ring is designed to decoratively cover the top edges of a 1.75 inch diameter hole, and particularly the hole in the oil lamp ceramic base
which may be found in this store. Both are designed for use with commercially available 1.5 inch diameter confetti oil lamp or LED lamp inserts. The ring can also be used to cover the edges of holes in other creative applications. It's thicker so it can be fabricated using the Shapeways porcelain process.
Various materials can be used to make bases for oil lamp holders into which the confetti oil lamps may be inserted - wood, stone, metal, plaster, concrete, or similar materials that can form a solid and stable base for an oil lamp. A shallow 1.75 inch diameter hole at the top of the base is required to allow the decorative ring to fit in place and a deeper concentric 1.5 inch diameter hole of an appropriate depth needs to be formed further into the base to hold the oil lamp in place. The porcelain material options are available for applications involving actual flames.
This is the source I use for confetti oil lamps but compatible parts can be obtained from other online vendors.
For non-flammable applications plastic material options are also offered. Other applications may include decorative hole covers for vases, hole liners for costume or steampunk applications, ventilation hole covers, and 10,000 other uses that I can't think of right now.
Two sizes are available but both fit into the same sized 1.75 inch diameter hole. The small version has a top outside diameter of 2.0 inches and the larger version has a top outside diameter of 2.4 inches for a bit more overlap.