Importing several product variations in one product display

I wonder what is the easiest way to import this, for example ring

RING SKU1 has 4 different sizes 5, 6,7, 8 size.......

For now I managed to import only one size via excel, other variations I have to do by hand.....

So for each size I would set the SKU to lets say......SKU1_5, SKU1_6, SKU1_7....etc....

But how to do this in excel.....
Becuase the product variations and product display import mapped importer communicate with each other with same SKU.....but here SKU changes........

Any idea?