Bought to replace the long strap of a Fitbit Charge 3. Fits the tracker perfectly. Color, texture and length are identical to the original band, but if you're picky the replacement buckle/latch is a grey metallic silver rather than the original silvery purple color.
Tested for 30mins/day for a week in water (heated chlorinated spa) and no change in the band or the waterproof characteristics of the Fitbit, so the mechanism connecting the band to the Fitbit isn't compromised. Seems all good.