Cheap Chinese knockoffs. (I doubt these ever list “$99” retail.) Functional, but the weights listed are about half what they say.
I doubled the “20 lb” band, and it just lifted a 10 lb dumbbell. I doubled the “25 lb” band & it reached equilibrium with a 25 lb cable.
Where I come from, double the band = double the resistance. So yeah, you figure that in depending on the type of exercise you’re doing. But it seems they’ve weighted these for always being doubled.
So tied to the (included) door frame wedge, one end in each hand (depending on the exercise) yeah, maybe. But not for single arm/leg moves.