Stock was set to gap-up. Tried to get in pre-market, could not get a fill. Orders filled at market open, price went all the way up to .17 from my purchase price of .152 When I tried to sell, momentum had turned and my limit order in the high .16's did not fill, as a result, I had to chase it down and finally got out at .1589 Lesson: when going long on a morning spike, sell into strength and use market sale if there is there is no risk of getting a bad fill.