From the Manufacturer
Because every ear is different, Shure sound-isolating earphones come with a broad assortment of sleeves to ensure a personalized fit, as well as proper sound isolation. This pack includes 100 reusable, disposable foam sleeves that compress to fit gently into the ear. Once in the ear, the foam expands to form a tight yet comfortable seal that holds the earphones firmly in place. These foam sleeves are sized medium for people with mid-sized ear canals (Shure also sells small and large sleeves). The sleeves are designed specifically for use with the E2c sound-isolating earphones.
Product Description
Because every ear is different, Shure sound isolating earphones come with a broad assortment of sleeves to ensure a personalized fit, as well as to ensure proper sound isolation. These reusable, disposable foam sleeves compress to fit gently into the ear. Once in the ear, the foam expands to form a tight yet comfortable seal that holds the earphones firmly in place. Medium size - choose carefully for the best personal fit. For use with the E2c Shure Sound-Isolating earphone.