firstly i'm no expert... i usually confine myself to asking questions rather than answering them but fwiw this might be one way to think of it:
product table (pk id)
id, make, name, type
1, adidas, samba, adult
2, nike, air, adult
3, new balance, 305, adult
4, nike, air, kids
sizes available (pk: product_id, size)
product_id, size
1, 5
1, 6
1, 7
1, 8
1, 9
1, 10
2, 8
2, 9
3, 7.5
3, 8
3, 8.5
3, 9
3, 9.5
4, 6
4, 7
4, 8