The Ear Tip provides a secure and comfortable fit in your ear, and prevents feedback (whistling). Your purchase of the Eva device comes with a 1-month supply of assorted tip sizes. You will need to determine the correct size for your ear before you order more. The Ear Tip lasts about 30 days, and costs about $1.50 each, or $3.00 per pack which contains 2 tips. These packs are available for purchase through our online store.