Tapered Caps & Plugs with Wide, Thick Flanges - WW SERIES Accepted by the aircraft industry, Series WW caps are designed with a wide, thick flange to insure against being erroneously forced "all the way through" when used as a plug. Now available in seventy-six sizes, this versatile part may easily be used as a cap or plug depending upon the application.Material: Low Density PolyethyleneStandard Color: YellowApplicable Spec: NAS 816