I always believed the TMBR fills are supposed to be instantaneous. I guess they are not... It happened to me once before a couple of months ago but I did not pay any attention and thought that was some kind of a glitch. Today it happened to me for the second time. I wanted to close an existing long position and placed a Sell market order routed to Smart. I did not get an instantaneous fill, so I assumed that TMBR did not take it and it went to NYSE. Not only that, TWS also showed the order to be live on NYSE. I did not get a fill for about 15-30 seconds. I did not time it, but I am absolutely sure it was no less then 15 seconds. During that time there was a print at the bid price and the bid went down 3 cents. Then I got the fill at the new bid price. To my surprise the fill was from TMBR. I am wondering what actually happened and whether I should expect this kind of stuff in the future? Did TMBR hold my market order until it was "willing" to fill me, or even worse, did they send the order to NYSE, then removed it and gave me the fill themselves? Either way I am not really comfortable with the situation, hope someone will explain what it is all about.