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My hand rests on the upper bow of my horn. What should I wrap around the upper bow to protect the finish?

Leather.

A black leather piece (lined), just like pro horn players and many trumpeters use (to see examples, look under accessories in most on-line brass music stores.

I meant something like this...

Wow, that's nice MSM! which side goes towards the tuba?
I've always had good luck with those wrap-around steering wheeel covers. Just cut it to the appropriate size and shape, wrap it around, and tie it off with the provided strings. They come in lots of colors and textures, too.
If you're worried about condensation, and don't want the hassle of attaching anything to the tube, try a Googalie (tm) here http://www.ibowtie.com/xcart/product.ph ... 252&page=1
I love mine, it's super soft and cleans anything. Just hold it in your left hand, not only will it protect contact points but you can clean the whole tuba with it!
/sales pitch
MF

Tennis racket tape has always worked well for me. I stole the idea from a horn player friend of mine. It's cheap, it lasts forever, and you can find it anywhere.

Thanks - most all great. Can't find a mall brachlet.

http://www.leatherspecialtiesco.com/
These guys can custom make you a guard. They are three layers: leather on the outside, plastic in the middle to stop moisture, and soft felt-like material on the inside that goes against the horn.