The Etymotic earphones come with several different eartip types, including these niftily ergonomic design. These Etymotic gray silicon eartips are fairly durable but like all great things, they too will pass in time. For whatever reason -- wear, tear, or just plain 'I forgot where I put them' -- you'll eventually need some replacements. These come in a package of 10 (5 pairs). Will fit the ER-4S/ER4P/PT, HF2/HF3/HF5, MC2/MC3/MC5, ER6i and EK models. NOTE: Eartips are NOT returnable due to hygiene/health concerns.