8 power, 21mm objective lens (the big one up front) diameter. Exit pupil (the column of light that hits your eye) is the obj lens diameter divided by the power -- so an 8x21 will have an exit pupil of 2.6mm. Sonce your eye's pupil gets up to a max of 7mm at night fully night adjusted, the classic 7x50 with its 7mm exit pupil is ideal. For bright daytime condition an 8x21 would work. I have two sets of 8x30 (3.75mm exit) binocs. It's a nice compromise of small size, adequate power and bright enough for most daytime viewing. YMMV
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Better is the Enemy of Good Enough.
Okay, what’s your point??