We have several possibilities for this.If you do not specify a size, we will send you the most common size. If that size turns out not to be a good enough fit, we will exchange it.You can also tell us the size. You can do this by sending us a picture of a speaker that fits you well. If you don’t have one, you can also use our measuring tool to measure how big the speaker needs to be. Or you can just send us a picture of the measuring tool at your ear. You can find the measuring-tool here.