I thought it would be easier to conceal but I guess it isn't Can anyone tell me what they use it for? Do you use it for other stuff besides a sponge ball routine?

it's often used as a "Final load" for a sponge ball routine.

Most magicians switch the other spongballs they're using out for the large one and then put it in the spectators hand (Making the spectator think that several small ones were being put inside) When the spectator opens their hand, viola! they're holding a giant ball...to their surprise!

Here's a tip;

Soak the ball in water and then ring it out before use. It'll make it MUCH softer and easier to squeeze. It'll also make it appear more lively and larger.

I dont know to meny people that like wet balls in there hands.

lol....

this is why I said to wring them out....they're not wet when you're using them...they're slightly moist and you're spectator cant tell...they just feel super soft...

I saw a friend of mine perform a regular spongeball routine using these big sponges. He had small and skinny hands and he liked to challenge himself by performing effects that he would deem impossible (or technically very difficult to do), probably because he was working at a magic shop at that time. I came there to visit him and we were talking about how it would look like doing a Two-in-the-hands routine with those. I never knew he actually practiced doing it until he performed it for a layman customer. He really got balls - no pun intended.