The O`s made their first venture into the qualifying rounds this season following relegation from the Football League at the end of last season, getting past East London rivals Dagenham & Redbridge in a replay, and now travel to SkyBet League One strugglers Gillingham as underdogs.
It`s a fascinating tie, despite the fact that neither side are exactly in the best of form at present.
The Gills are currently under the caretaker leadership of Steve Lovell following the short tenure in temporary charge by Peter Taylor.
And Lovell knows all about football outside the Football League, having recently been number two at Bromley and been in charge at the likes of Hastings United, Sittingbourne and Ashford Town in the past.
Both teams have struggled in their respective leagues, but will aim to use the cup tie tomorrow as a possible springboard to more success.
The O`s will be buoyed by the fact that Gillingham haven’t won on home soil since September 16th. However, Steve Davis`s side`s last victory came in that replay win over the Daggers on October 17th.
A potential problem for former Crewe Alexandra boss Davis is the number of loan players he is currently using will mean he may be forced into making changes.
Davis blooded several young players in the ties against the Daggers and some of those are expected to feature again tomorrow.
Mark Ellis and James Brophy were unable to play against the O`s East London neighbours due to terms in their loan agreements from Carlisle United and Swindon Town respectively, and it is expected the same will apply tomorrow.
There will be some familiar names for Orient`s visiting fans in the Gillingham side, including goalkeeper Stuart Nelson, who played 30 times for the O`s in 2007/08, while defender Gabriel Zakuani started his career at Brisbane Road and went on to become a firm favourite with supporters in making 87 senior appearances before being sold to Fulham for £1m in the January transfer window of 2006.
Two others in the Gills squad, defender Luke O`Neill and midfielder Scott Wagstaff, had loan spells with Orient in 2015 and 2012 respectively.