Made from glass filled nylon, the Thin Electric series have thin, undercambered blades for high thrust on electric motors. All props have a 0.25" bore with adapter rings for 0.128" (3.2mm), 0.158" (4mm), 0.197" (5mm), 0.237" (6mm) and 0.313" (8mm) prop adapter shafts. These props should not be used with glow or gas powered engines. Maximum RPM is 190,000 / Prop Diameter in inches.