SRAM red 11-25 casette and shimano DA back wheel

odichu Posts: 116
edited August 2010 in Workshop
so I slipped the cassette over the driver of the hub like says in the instructions leaflet but there's a 3-5mm space on the driver which obviously allows the cassette to move back and forth.

1) I'm guessing I need some kind of spacer? there isn't one in the box...
2)Why does it not fit exactly in the first instance?
3)Where do i get spacers from?