336 diodes at 660 nm red and 850 nm near-infrared across the whole scalp, in a foldable cap that runs wired or on a battery pack. This is the dose format the randomised trials used, not a comb you drag across a parting.
Low-level light therapy for thinning hair has the best evidence of any at-home hair device after minoxidil. It also takes three to six months and it reverses if you stop. Both of those sentences are on this page for a reason.