This card can allow "Number 91: Thunder Spark Dragon" to use its stronger effect.This is the first card in the manga to allow an Xyz Material to be re-attached.which works very good with Number 91: Thunder Spark Dragon to make the maximum usage of it effect 

So far there are only 4 cards in the game that can help Number 91: Thunder Spark Dragon use its second effect: "Overlay Eater", "Xyz Unit", "Spirit Converter" and "Overlay Regen". The latter two are the most recommended, as "Spirit Converter" can attach more that one monster as an Xyz Material, combined with easy swarm capabilities, while "Overlay Regen" is very easy to use, as it becomes material itself, making it a quick means of gathering the materials needed.

The Thunder family can help Xyz Summoning this card, as well as being available targets for "Spirit Converter".