The infinity top is magic armour from the infinity robes set worn in the torso slot. 55 Defence is required to wear the infinity top. The infinity top can be obtained as a reward in the Mage Training Arena minigame by giving the Rewards Guardian 400 telekinetic, 450 alchemist, 4000 enchantment, and 400 graveyard pizazz points without any Desert tasks discount.
These robes can also be changed from their original colour into the colours of the elements (fire, earth, water, and air) with the help of rune guardians.
A dragonbone upgrade kit could be combined with an infinity top to make a dragonbone mage top. This is a cosmetic enhancement and does not change the stats in any way.