Why would anyone manufacture a 10.5x45 instead of the standard 10x42 model? Being cynical, perhaps, we'd say it's one-upmanship. However, a 10.5X does have 5 percent more magnification than a 10X, and a 45mm objective gathers 15 percent more light than a 42mm objective. The respective twilight factors are 21.7 and 20.5, which perhaps explains why this Weaver Grand Slam glass outperformed the 10x42 models in low-light performance. Mike Parsons described it thus: Very clear, well-made, not too heavy, nice twist-out eyecups, and the price is right.