You or your mechanic use them to adjust the gap between the rockers and the valves.

Mike

Essentially all the engines share exactly the same basic design, but the different series use different sizes.
All the aircooled engines (bar the 800/1000) have the same basic size.
All the watercooled engines (+ the 800/1000 aircooled) have generally thinner shims than the aircooled engines.
The bevels generally have thicker shims, of exactly the same design !

I started out by buying small selections of used shims but now have a set of shims for aircooled engines and find that I use a very small proportion of them, so would definitely consider buying in some more and offering an exchange deal for a small fee (to ensure I dont lose money cos the cost of a set is not small as you probably know)

What do you think would be a good deal ?

From experience, i'd suggest going to a dealer and measure the shims you're buying with the same equipment as you've measured your existing ones with.
I've sent shims out mail order only to get a phone call saying i've sent the wrong ones out only to find they've been measured with different equipment to my own, especially closing shims. There's also some "tolerance" on the new ones to and if you're shimming tight, to old fashioned tolerances, you could have problems.

:)
Isnt DIY wonderful ;)

And get back to work nelly or I'll tell your boss you're slacking :o