The outer diameter is 3mm, the inner diameter is 1.5MM.
the hole behind the small speaker of the earphone is used for tuning, or the earphone shell is punched, drilled, and the front cavity is opened. Y1 density, Y4 density, in order, the density of Y1, Y2, Y3, Y4, Y5, Y6 is getting higher and higher, and the air permeability is getting smaller and smaller, so Y1 and Y6 are not commonly used. The most commonly used are the three types of Y2 Y3 Y4