Vortex Optics Defender Scope Eyepiece and Objective Lens Cover - E-10 p New for 2016. 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. The E-10 cap is has three stop positions. The first vertical, to put your dope disk (optional accessory) literally right in your face. The second at a 45 and the third at 90 to lay flat back. The E-10 fits all Vortex Riflescopes except the 1-inch tube Viper model VPR-M-01BDC, VPR-M-04BDC and VPR-M-03BDC. Outside diameter: 40-46 mm | 1.57-1.81 inches