(25) Pieces Top Secret PDR seals are designed to effectively plug electrical knock-outs. Molded in BLACK the plugs conceal knock-out holes in steel boxes and other metal enclosures. Recognized under the Component Program of Underwriters laboratories/ NYLON6/6 Flammability: 94V Material Temperature Index: 125º C; maximum temperature not to exceed 105º C. Attractive silver Black color Economical protection Designed with locking fingers for a secure fit Material: 6/6 Nylon Color: BLACK Please Note these are trade size Plugs for use in 1/2" KNOCKOUTS NOT.500" HOLES