Product review (3 stars): I have a 24' long dryer duct with 4 90 ...
I have a 24' long dryer duct with 4 90 angles and could get the shaft to feed only past the first angle from either end (inside the house from the dryer and outside on the roof). I had to guide it by hand past the first turn at each end,  but once inside the duct it wouldn't negotiate the next 90 turn or go any further. While it did loosen a bit of lint from either end, the majority of the duct is still restricted with lint.