From 7 to 8.5 power. But I do not like the 7x50 size which is mostly used for maritime work. Pretty heavey and some edge field distortion inherant in the design. 8x40 or 8x42 seems about perfect. THIS IS IMPORTANT!!! Instead of buying more magnification, just spend more and buy better optics. You can see more detail with a set of high quality 8x42's than with a set of cheap 15x40's.
Probably the best bino for the money are the SWIFT AUDUBON 8.5x42 (model 802 I believe) at $279.99 on Binoculars .com
Swarovski and Leica are probbaly the best period though some would say zeiss. But the Conquest binos are not as good. You can get a better bino made in Japan that the Conquests (which are made in Hungary).