Sizing of hybrid bikes is far less critical than sizing of drop-bar bikes. That's why even better hybrids are generally offered in size increments of 2 inches or more whereas high-performance drop-bar bikes usually come in 2-cm increments at most. At about 5'8" or so, I could easily accommodate anywhere from a 17" to a 20" or 21" hybrid, though the 21" might be a bit tight in stand-over height.