Bicycle Mechanics - SRAM Force 2010 cable housing question

I'm just installing the 2010 Force brifters on my bike and there are a couple of weird things.

1 - they supply two different types of cable housing. One looks 'normal', but the other is slightly thinner externally and looks to have a braided wire internal sleeve instead of the solid tube of the normal stuff.

2 - ferrules are in two sizes. Same external diameter, but the 'SRAM' branded ones only fit the thinner cable housing. The plain black ones have a larger internal diameter and fit the 'normal' cable housing.

So - is each type of housing for a different use? One for the brakes and one for the gears?

The thicker cable & housing - usually 5mm - is for brakes. The thinner - 4mm - is for the gear-cable. Don't mix them up. The ferrules are for what they fit.

Thanks.

Wish they would attach better instructions!

<edit>
Lots of 'presumed knowledge' here (not mentioned in my bicycle maintenance handbook either). I looked on the SRAM website for some installation guides, but what was available was the same as the printed versions that came in the box.

I guess I should come clean and admit that I already had one brifter installed using the wrong housing (thicker brake stuff on gear cable) before I realised.

When moving to the next brifter I picked up a ferrule and it didn't fit the housing...WTF...so I started to examine everything in more detail and I realised I had two types of housing. Size difference is not easy to pick by eye and I would not have noticed if it was not for the ferrules.

Fixed for second brifter and enough spare housing to go back and fix the first one.

Bike at LBS now getting the bottom bracket installed (don't have right tool) and the steerer cut (somethings you leave to the pros...).