This is the last flip cap you will ever need! Virtually indestructible, this cap will fit snugly on nearly all Vortex Optics and features a snap flat spring that will keep your line of sight unobstructed. Outside diameter: 48-53 mm | 1.89-2.08 inches.Specifications and Features: Outside diameter: 48-53 mm | 1.89-2.08 inches Features a snap flat spring that will keep your line of sight unobstructed, and tabs on each side for quick open or close Great fit, this cap will fit snugly on Viper PST (PST-210S1-A & M) Viper HS (VHS-4303 & 4305), Viper HST (VHS-4308 & 4309), Diamondback HP (DBK-10019 & 10015) and CrossFire II (CF2-3016 & 31013) Virtually indestructible