Reply To: different tiers or gradations to various child products

I have a variable product (Sports floor) with three children’s products. 20mm, 30mm and 43mm bottom thickness. It is one and the same floor. But now the products have different discounts. So:

100x floor 20mm => 10% discount
100x floor 30mm => 8% discount
100x floor 43mm => 7% discount

Just my question: How can I give the different child products different levels? My idea would be to create a separate rule for each Child, but then I have to enter the Child product ID.