Objective Lens: 42mm
Eye Relief: 17mm
At first I really couldn’t tell much difference between these and my old Vortex Diamondbacks. But, when I tested them side by side at dusk, the difference was night and day, literally. Looking through the Vipers felt like someone turned the lights on! They have far superior light gathering ability. Also, edge to edge clarity is much better than the Diamondbacks. The build quality is better as well. Smoother, more positive eyecups are the obvious upgrade over the Diamondbacks. A locking diopter is nice since you only need to mess with that once. Overall, I’m very pleased with the Vortex Viper 10x42.