Heff & I both have a pair of Black Diamond trekking poles. We love them because of the Flick Lock. The Flick Lock is similar to what is on a lot of tripods. They hold the sections of the pole in place and adjustments are very quick and easy. I definitely agree with Ear Mountain when he said
Good poles are expensive but the better ones are: lighter, more ergonomic, have an anti shock feature, easily adjustable, very strong and will last a long time. If you are planning any off trail trekking get the best poles you can afford.
Like Hockey Ref, we bought ours for half price on Ebay. We love them! We like the cork handles because when your hands get sweaty, they absorb the sweat, which means they also absorb a lot of salt. We usually have to bring the poles in the tent due to hungry Mule Deer.
Poles also keeps my hands from swelling while hiking.