Like sprstpd said, an order for 100% of the total opening print volume will almost always move that print, unless you happen to be in the same position as the spec would have been if he had to step in, and the spec is honest enough to stand aside. In the case you cite, that means there would have had to have been buy orders totalling 1600 shares, and just the spec selling those 1600 shares at the open. Your sell order for 1700 shares, had you given it to him, would have caused the spec to stand aside, and you would have sold 1600 with 100 remaining, or the spec would have taken the extra 100 if wanted, or he might have marked it down to 0.67 in order to fill the whole thing. Any other scenario, like 1600 in buys and 1600 in sells, with the spec not involved, and he would have taken the thing down at least 0.05 in order to buy your 1700. And this is a fairly tightly collared stock - other, more volatile stocks, and you're going to give up a lot more. What I meant by missed opportunity was to question what you miss by just giving the order to the spec. In this case, with a stock that is so incredibly illiquid, if you really have to trade it, you really have no choice but to give it to the spec, because he's the only guy that gets any order flow. The only way you'll get filled on an ECN is if your order is mis-priced and can be picked off by the spec or an arb - there are almost never natural buyers or sellers on the ECNs for stocks like this. Forget about saving pennies - you're going to get picked off for a few cents and you just have to live with it. Much more in a stock that has some wiggle to it.