If you buy earpads for Grado, later in the purchasing process I will ask about this diameter:

This is my 325e, measured through the middle of the earcup, from edge to edge: 54mm

If you buy earpads for Grado, you will receive 2 pairs of foam inserts! They are of different densities and so the overall sound will be different. Try them both and see which one you like best.

You are responsible for paying any fees when these products enter your country. Some names I heard of are: customs fees, duties, taxes, handling fees. These depend on the regulations of each country and I can't possibly advise you on it. If you think they may be a concern, please check with your Customs. Usually they have that info on their website.