There are 28, 32, 36 and 65cc models. The cooling fins are bigger on the 36 than on the 32, otherwise they look the same. I don't have any 28s. I just finished a 36 for a buddy but am still breaking it in and so I haven't tached it yet. It definitely felt more powerful on the stand, though.
Do you know the model# of the weed whacker it came out of?

J