Product review (5 stars): I recommend these as they worked great for me.
Had regularly cleaned my roof mounted dryer vent with the shop vac and always got a good bit out. Just used this and was surprised on how much (extra) lint came out. I feel much safer now as to not having a fire caused by lint and the clothes dry faster.
Read some reviews that urged caution and the possibility of twisting /breaking off these while in the wall.
I had no problem with these. Used a variable speed drill on a very slow speed and slowly inserted each length into the vent. Once I inserted two additional rods, I'd pull them back out to suck up the debris. Then go further.
Do not put the drill in reverse as the rods would unscrew from each other and then you'd have a problem.