there is not a lot of difference, the uniphoxx is a bit thinner and sits better in the hand, but I have small hands. I only use 9.5mm steel, try balls of steel, they are online, or look on Ebay lots on there. if you buy the kit the bands and 8mm balls are well matched. practice with that setup, later you can go for thicker bands and bigger ammo, I like a lighter setup for hunting as my wrists are fxxked.