1. About 6CM (as long as the diameter of the ear cotton originally equipped with your earphone is around 6CM, it can basically be used, the error of 5mm is okay, larger earphones are fine, the ear cotton itself has a certain flexibility)2. The sponge cover has three functions: one is to prevent slippage, the other is to prevent sound leakage, and the third is to prevent resonance between the earplug shell and the ear bone.3. There are small pronunciation holes on the earplugs. When you put the earplugs in your ears or put them outside, it is very likely that dust will enter the earplugs through these small holes. The earplugs have a very thin diaphragm, only a few Micrometre, a little dust will change the vibration of the diaphragm, which will affect the sound quality and even cause the damage of the earplugs.The earplug cotton can block these external debris from entering the earplugs and protect the earplugs.In summary, the sponge cover of earplugs is very useful, please stick to itColour: blackMaterial: spongeSize: 6cmPackage Contents:20 x Earphone spongeOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.