|80% carbon fiber, very lightweight
Each pole has a pair of flip locks with large pressure-adjusting screws that let you change the length of the pole from 24" to 52" (61 to 132 cm). At 5'10" tall (1.78 m), I have mine set to either 46" (115 cm) or 48" (120 cm), which gives me a nice, ergonomic arm angle at my elbows. I've read that 2/3 of your height is about right, which is consistent with my own findings. If I'm going TO work (downhill) I'll make them slightly longer; if I'm coming home FROM work (uphill) I'll make them shorter. Either way, you can tell if they're too long because the tips will drag on the ground.
The first word that comes to mind, after using them for a week, is: stability. Having two extra points of contact with the ground, I feel much more balanced and steady on my feet - not that I was rolling around like a drunkard before, but I can imagine it will be a lot safer in the snow and ice of the coming winter. You can take off the rubber tips and leave durable tungsten steel tips that will be really helpful in staying upright.
The second thing I noticed: speed. With the consistent rhythm that you employ with your arms, you increase your speed, almost without noticing it. My time to walk home was reduced from 28 minutes down to 25 minutes one day, which was fantastic. I wasn't stopping as often to catch my breath because I was able to use some of my upper body strength to push myself forward. Carrying a heavy load was also slightly easier.
I wasn't sure how easy it would be to get a good rhythm going, and to avoid tripping over the poles. As it happened, the rhythm came naturally (two steps for every pole movement) and they are lightweight enough that they are easy to place accurately, even when walking at a normal speed. So far I've only had one minor incident when the flip lock wasn't tight enough (hence the adjustable thumb screw) and the pole shortened itself while I was putting weight (pushing down) on it. It was trivially easy to tighten the screw and flip the lock back and carry on.
I added some reflective tape to my poles since my morning walking, and soon my evening walking, is in the dark. At this time, I'd say that my $50 was well spent. The poles do what they were designed to do. Despite their super light weight they seem pretty durable. I shall continue to use them on a daily basis and look forward to taking them with me on the PCT next May.