If yours are the same as ours, they're 125 mm diameter with a hole for an M10 bolt (11 mm hole).  In the US, they're available from BoatZincs, where for some reason they're marketed specifically for Azimut boats, but they're the perfect size for us.  The R5 is almost the right size as well, but being imperial, the hole is slightly too small and must be drilled out -- lots of people do this, but it's a pain when you can just get the right ones.