These wicks are amazing for optimum crackle and melt pool. Definitely size down though, I use a coconut soy wax and got the 16mm for my 9cm diameter vessels and the wicks are too big and I have a lot of soot throw so I need the size smaller. It makes sense considering there is double the burn power as it’s two wooden wicks put together and the flame is a lot larger than a normal single wick. Beautiful made, easy to use and the wick tabs keep them perfectly in place. I found trimming them to size before assembly was best and putting the trimmed end at the bottom in the wick tab best for aesthetics if anybody is struggling with trimming post-pour.