By habit, we try to shove earbuds into our ear canals in attempts to get them to stay in. The 500 Series headphone is a completely different concept. The tip of the enhancer (ear tip) should funnel gently down into the ear canal and the base of the enhancer should fill the entire concha (bowl) of your ear. If there is still quite a bit of space between the back of the enhancer, and the back of the bowl of the ear, there is nothing to support it and it will eventually fall out. Typically larger sizes will fill the extra space inside the concha. We recommend trying both sizes featured in the packaging. If you are still experiencing fit issues, please reach out to your local JBL Customer Support for information regarding different sizing options.