For some reason, I think this may have gotten left out of the conversation. When purchasing a bowl to go with existing bowls, it's a good idea to know what tuning system you're in. There are two tuning systems: 440 Hz or standardized tuning, and 432 Hz. 440Hz is what the orchestras tune and is a good tuning to have if you play with other instruments. These two tuning systems are based on the note a being either for 440 Hz or 432 Hz, and then all of the intervals of that scale are measured in a way to create that tuning. So in purchasing bowls, it's good to know which tuning system you have then if you ever break one or want to add others, you can match it up. My bowls are all in 440 Hz, however, when I broke my A bowl, I decided to move toward 432 Hz. The tuning that you have already or choose to have doesn't really matter, except that what ever tuning you choose, it is nice to keep them tuned all together. Remember you're the healer not the bowls.