Hello [member=kellen] and welcome to the forums.
What you describe above doesn't actually tell us how you want to use this.
The most straight forward way would be to have a table products with fields id, name,quantity, price
e.g.
100,A,375ml,20$
101,A,500ml,30$
102,A,750ml,50$
103,B,125ml,13$ etc
Then if we assume that you want to somehow use these, let's say for sales then by using the set_relation and with a "{name} {quantity} {price}" the user can select the one he needs.
Caution though, this is not the most optimal way of doing it. For such a configuration you should have two tables
products and product_details where the qty and price go to the product details.
If you choose to have 2 tables products and product_details then it will need a bit more effort to get it right since you will have to fetch information from two different tables.