I was looking through some misplaced jars from last year and came across this. I found the gall (we've been calling them oak apples) under an oak tree, a black oak, I believe, but we have white and black oak, so it could have come off either. Five wasps emerged from the gall, unfortunately, I didn't know that until well after they died. I still have the gall and the wasps in the event more pictures are necessary.

The gall is 50mm across and the wasps are 5.5mm, in their slightly curled state.