Greg Heidt wrote an answer about LEKI Pro Carbon Cross Country Ski Pole on January 19, 2010
First off, these poles are very lightweight (expensive) and are geared more towards advanced skiers. That said, if you are an intermediate skier who is motivated to get faster, these could be a good choice for you. A lighter pole will feel easier to swing and allow you to reach a higher tempo.
These poles are one size: 180cm (almost 6 feet). Once you determine your desired length, you remove the grip with heat, cut the pole and re-glue the grip. If you don't have experience with this process, you would be wise to let an experienced person take care of it for you.
The length you will need depends on the style of XC Skiing you do, your skill and your height. In general, classic poles are shorter and skate poles are longer.
For beginners and recreational touring, the pole should fit under your armpit.
For advanced classical skiing, choose a pole that reaches the height of your collarbone.
For skating, poles should come up between your chin or lower lip. Some skate skiers prefer even longer poles.
These are recommended lengths but as you develop your own style, you may find that slightly more/less length is right for you. If you are a skate skier, you will definitely benefit from the lightweight poles. The weight will be less noticeable for classic/touring.