Everyone knew so what was the point of answering? Still, Blue raised her hand anyway. "The undetectable expansion charm has two effects. The first, like many of my other classmates have so kindly pointed out," she nodded at a few, trying to be polite and formal because that made class a lot more interesting just cause it did. "is to make the object's internal space bigger than the object itself. The second is that the charm disguises the object so only the witch or wizard who cast the spell and anyone who the spell-errr or castor tells can see the inside."

Yeah. Something like that.