5mm anymore that would have been powerful enough. The bass sounds better now. The compartments are made of mesh fabric while the base is of solid fabric. The previous owner used mostly nails and in the past I have used some of the metal strips with bendable tabs. Its not small enough for my ears unfortunately. Here, the foam rises above the water line. This certainly is not. Might be just my pair, who knows. this is the third time that I put it together , two times with pipe thread seal tape and didn?t hold The reviews here either wavered on being too big or too small so I actually walked into a Crocs to try them on but only found size 9 and 11.