In reply to DaveHK:
Alpkit do some adjustable carbon ones that fold into 3 sections, as do Harrier. They are robust enough to allow you to vault small streams / puddles. Pop into one of their shops and try some.
Carbon and alloy have different qualities. Alloy might not be as light or fold up as small. On the other hand, if you get the end stuck in a crack, they will bend not snap when travelling at speed. Handy if you have miles to go or they are the main support for your ultra light tent. Fixed poles have different grips, that some people prefer. The idea is that your arm should be about a right angle. Its not an exact science, just what feels right.
Top tips. If you wrap 1m of gaffa tape around each one, you have an emergency stash of tape. Handy for fixing rips in tents, jackets, first aid etc. Also, 3M Diamond Grade reflective tape, from that auction site. Its the stuff you see on emergency vehicles. Wrap some of that around you poles, so that when you leave them against a wall or in long grass at night, you can find them again. If you're racing and there are 100 pairs of poles outside the checkpoint, it allows you to find yours quickly.