Pentaconn COREIR Brass Metal Core Eartips for In-Ear Monitor IEM Earphone We have adopted BRASS, a material that is closely related to sound, for the metal core. By maintaining the shape of the sound conduit, the consistency of the sound is also maintained.Prevention of collision between the earphone nozzle and the metal coreWe prevent collisions between the earphone nozzle and the metal core by placing cushion parts made of colored silicone on the metal core. The cushion parts are color-coded in CMYK order by size, making it easy for most people to distinguish neighboring sizes. Specifications: Material: Silicone Metal core: Brass with nickel plating Compatibility: Fit for 4.5mm to 5.5mm nozzle size of IEM earphones Outer Dimensions (Please refer to the attached picture for details): S: 11mm MS: 12mm M: 13mm L: 14mm 4 Different Sizes: Small (S) - 2 Pairs per Pack (Black) Medium Small (MS) - 2 Pairs per Pack (Blue) Medium (M) - 2 Pairs per Pack (Yellow) Large (L) - 2 Pairs per Pack (Red) Notes If strong force is applied to the metal parts used in this product, they may come off from the silicone parts. The metal core of this product is made of brass material with nickel plating. If you have allergies or are sensitive to your skin, please refrain from using it. If dirt adheres, wipe it off with a dry, clean cloth.