Hard dart flightsare made of a stiff polyester plastic that holds shape well. The layers are permanently sealed together by heat during manufacture. Because the plastic is harder, they don't tear as easily as soft flights, however if they do tear, they cannot be resealed and are ruined.
Hard dart flight does not flexible like a soft flight when hit, but do "pop off" the shaft when hitting another dart. This is desirable as it reduces deflection and allows tight groups.
Hard dart flight originally is made of a clear plastic, which resulted in fairly dull colors in printed designs.