Greater satisfaction with minimum investment on your earbuds Normal hardness focuses on the expressiveness of sound 10mm length of inner shaft for standard earphones.(inner hole from 5.4~7.2mm of diameter) Medical grade silicone offers in-ear stability and a lasting comfort Various option of size by analyzing the shape of more than 1,500 ears over two years. (L-Large / ML-Medium Large / M-Medium / MS-Medium Small / S-Small / SS-Small Small) "SednaEarfit" series is replacement earbud tips developed by analyzing the shape of more than 1,500 ears over two years by AZLA Inc. Based on sophisticated and many data, SednaEarfit offers six kinds of tip sizes to give the best sense of fit. (L-Large / ML-Medium Large / M-Medium / MS-Medium Small / S-Small / SS-Small Small) Using a dual structure with different hardness, it prevented sound deterioration due to resonance and prevented easy separation from earbuds. A horn-shaped internal structure that directly transmits sound waves to maximize high frequency characteristics. There are four variances in the SednaEarfit series, depending on the hardness and the length of the inner shaft.  SednaEarfit / SednaEarfit Short / SednaEarfitLight / SednaEarfitLight Short Package includes : 2 Pairs (4 pcs)