The Rail Pass comes in two varieties, one for each class of service, Standard Car (普通車 Futsūsha?) and Green Car (グリーン車 Gurīnsha?) (first class car). Furthermore, the pass is time limited based on the length of pass purchased. Three time periods are available: seven-day, fourteen-day and twenty-one-day passes, which provide the user unlimited use of JR transportation services.
I bought the "Green Car" 7-day JR pass for a little over $200USD. Remember that you can only get these tickets outside Japan. Just flash the ticket, and if there's room in the Green Car (very luxurious way to travel), you're on the train. In my case, I can go anywhere in Hokkaido for 7-days.
I basically brought my information at the Sapporo JR train station to get my 7-day ticket, and away I went.
Remember that the Rail Pass is sold by the JR Group, it is obtained by purchasing an Exchange Order from a travel agency located outside of Japan. The exchange order can also be purchased from Japan based airlines such as Japan Airlines or All Nippon Airways. The Exchange Order cannot be obtained in Japan.
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