These are one piece, and easier to use than the two piece rigid plastic moulds. Cooling wax inside the mould can harden and distort the shape of these sometimes. Most manufacturers recommend that you not use beeswax for rubber moulds because it damages the moulds. Hard rubber moulds. These are not as long lasting as the other kinds of moulds and can be more expensive.
Results are good and they are very easy to use.
Acrylic and Plexiglass moulds, and Glass Moulds. I have never used this type, but books have indicated that they are easy to use, and produce excellent quality candles. I have had good success with just sticking the herbs or flowers on the candle after it comes out of my metal or home made mould. Other moulds and containers. Wax coated frozen juice cans.