Colnago Nemesis stem question

[RobJ]

I picked up a Colnago Nemesis stem for my current build and it didn't come with any instructions. Usually not a big deal - it's a stem, right? Well the Nemesis includes what appears to be a shim or in their terms a spacer. I can't find any information on what it is supposed to accomplish or how it affects fit. At first I thought it was for 1" steerers but the description below from one of the retail sites proves otherwise. Anyone have insight?

"a dual-mode stem that features an offset-bored spacer that sits between the steer tube and the stem. It gives a full range of adjustability and facilitates finding the perfect fit."

[mattr]

I guess it's a two position spacer to give two different lengths 5 or 10mm apart?
Either thick side forward (long stem) or thin side forwards (short stem)

[Zakalwe]

It's for adjusting the stem angle, rotate the spacer to alter the rise between 7 and 4 degrees

[mattr]

Ahha. A man who knows.

Bad guess on my part.

[coriordan]

So I have just bought a C59 (see introduce yourself) and I has come to my attention that it doesn't have the shim under the stem.

Is this a disaster (i.e is the steerer tube diameter now too narrow to be sufficiently grippy?). It's hard to describe exactly how the tightening bolts do up, but basically one side of the stem overlaps the other. I guess the idea is that with the shim and varying rotations, depending on your stem angle, it can always be lose or tight enough.

Anyone know where I can get a spare one (in the UK?)

Thanks