A
I agree, definitely the base of a mic stand. I also agree it's probably there to keep is rack tom balanced flying off its stand. That looks like a big tom. I get that sometimes with my 13" but I've got a cymbal on the same stand that works to balance it out.it looks like the base of a microphone stand. i don't know why it would be there unless it's used as a weight to keep the cymbal stand from falling over.