What does the ultra rumble pack do for the new R4 DS ultra

it is a slot-2 cartridge that can be bought with an r4 ultra; it will make a small "ruble" or shaking when you turn on the ds, start moonshell, or at certain points during compatible games (like a car crash). It is important to know that the number of compatible games is low, and that it makes a small noise when it "rumbles".