Bicycle Mechanics - Titanium Handlebar "shim"?

Hello,

I have flat titantium handlebars on two of my bikes and they both came with a plastic "shim" of some sort. I've left the plastic pieces on but what is this thing for? I know that titanium parts aren't suppose to be bolted to each other but my stems are not titanium. I *do* have bar ends on the bikes-- should I have some kind of similar barrier between them and the handlebar? I'll post a picture if necessary.

Chuckie

Aluminum and Ti fuse together over time... for a Ti seatpost I always use anti-sieze (not grease) to prevent this. Never used a Ti bar, but I would probably do the same for a bar as a seatpost... not sure about the plastic dealie though.

I have a TIBAR bar. Is the spacer black? The diameter of the ti bar is smaller and the shim may just make up the difference. My spacer is aluminum. Other material bars have a bulge. The ti is harder to form. It's probably much cheaper to use a shim than to bulge the bar, if it's made from tubing. Ti is very costly so that making a bulge may make the bar to pricey.

Also aluminum tubing will not squash as easily under pressure. I can actually squash my ti seatube on two of my ti bikes by tightening the front derailleur clamp too much.
It also happened to a friend. I can actually slightly squeeze the top tube on one of my ti bikes by hand.

I had aluminum bar ends on that bar for a couple of years with no problems. That leads me to believe it's just a shim to make it the right size. I have had ti bar ends on there for the last couple of years. No problems.