TubaForum.net

I don't know where it came from, but it looks like a gigantic model of dent ball from one of those 100 dent ball sets (.250" - .750"), except that it's 3 inches long, two inches in diameter (at the center/largest), and is drilled out to c. 1/2"...again: same basis shape as those tiny dent balls, but huge.

I hold it in the palm of my hand, and (whack!) it offers me some pretty epic head starts on really beat-up metal sousaphones, particularly the body/bell elbows and as far as I can reach down into the 1st branch with my arm.

When the small sides of bottom bows are not much larger than that diameter, it's save me (along with annealing) from removing tuba bottom bows with their small sizes (even at the connector joint) were crushed in (with a stacked pair of 1-inch magnets)...as long as the tubas were lacquered brass, and not silver...as I could refinish the area that I annealed.

I've had it/used it "forever".

I’ve used a good sized dent ball using the “whack from the inside” technique with good results also.

The fact that it is symmetrical and egg-shaped or perhaps I'd say (white) acorn-shaped really helps the thing to do a good job.