Is it possible to set attriputes in such a way that the customer can select the size on the product page?

What I mean is I have a cart that sells, among others, clothes. I want to load one product and allow the customer to chose form certain defined sizes for that product. The size does not affect the price, it is merely for ordering information purposes i.e. the price does not change.

Basically I don't want to have three items all the same product and price but different sizes, Ijust want to define a range that the customer can pick from (differnet for different products).

I don't know if this is simple to do or not, amazingly its something I didn't think of until I started loading items and so I havn't really explored attributes that much but it looks fairly confusing....
thanks for any help