I don't use trekking poles, I cut me a "staff" either from alder or an evergreen. They need some drying and it can be a pain to find one that is sufficiently straight, and doesn't have major flaws, like a big knot, but they take all the weight I can put on them... even when I jam it into the slope horizontally and lean on it. When you are traversing a steep scree/shale field it is a lot easier to hold one pole horizontally and provide balance and support that way than having two poles one of which is too short (the down hill side) and one of which is too long (the uphill side). On downhills I hold it behind me, and again it takes the full weight. I postulate that no trekking pole can take that abuse. They are all fine when the force is straight down, from grip down to the tip, but not when the force is trying to bend or break it, as it would be the way I use my "staff".
Call me old-fashioned, I tried trekking poles. They don't work for me. Unless I'm out on snowshoes.
Frans