So excited for my mod mic! If they ship the rest tomorrow, I have a chance of getting mine by the end of the week! I bought mine specifically for my HD558s, but I bought a few extra base clasps for any future headphones I get. Hopefully my HD558s will still fit in their case with the base clasp on, but if they don't it isn't too big of a deal. I don't travel with my headphones that much.