There is probably a real simple answer to this question. Maybe I just don't understand ARCA well enough. Below is my question to OX Customer service and their lack of response... -------------------------------- ARCA .vs. Quote Box? Just curious. I just placed a "large" limit order for 1500 shares of IEI at 113.80. Immediately after that, the bid on Quote Box correctly showed 113.80 (15). However the ARCA best Bid was something like 113.68. The Ask on both ARCA and Quote Box always agreed. This discrepancy did not clear up until my 1500 share limit order was completely filled. After that, ARCA and Quote Box happily agreed on both bid and ask. Please explain. Thanks, Todd K. and their "response"... Hello Mr. K., I understand that you said quotes on ARCA and the quotes on the quote box show different things, when they normally are the same. I apologize, but I am not able to go back and review or tell why the quotes were different. If this happens again please feel free to contact us as soon as you can so we can research this for you as it is happening. I apologize for any inconvenience this may have caused you. If you have any other questions, feel free to reply to this email and Iâll be happy to help. If you prefer, feel free to call us at (888) 280-8020 or click on the Live Help link found on the top right corner of our site. Phone assistance is available Monday â Friday from 9am until 10pm ET. Live Help is available Monday â Friday from 8am until 10pm and on Saturday from 10am until 2pm ET. Thank you for contacting optionsXpress and have a great day. -------------------- Is there a simple explanation for this? Thanks, Todd K.