单向双向：某些产品的手续费只在开仓时收取，有些则在开仓和平仓时都收取； Genius is the ultimate source of songs know-how, established by scholars such as you who share info and Perception concerning the tunes and artists they appreciate. 今日持仓/昨日持仓：中国期货通常指定平今仓和平昨仓