Box of 100 - Fixed, Square-Wire Spring Creates Its Own Threads Maintains A Secure Positive Grip That Will Not Relax Over Time; No Pre-Twisting Required Positive Grip Design Provides Fast, Easy Installation; Deep Skirt Helps Protect Against Flash-Over; Reusable For Easy Circuit Changes And Additions; Tough, UL94V-2 Flame-Retardant Shell Rated At 105 Degree C (221 Degree F); UL Listed To 486C And CSA Certified To C22.2 #188; Comply With Federal Specification W-S-610E