Matthew O'Boyle and Annie McCullough caught the eye at the Apex Clinic Ulster Indoor championships at David Lloyd yesterday.
O'Boyle and McCullough both enjoyed two victories, with the Windsor club girl causing an upset in the under-18s when she defeated number two seed Lucy Octave.
McCullough defeated Suzanne McKinstry 6-1 6-0 to make the quarter-finals where she engaged in an exciting battle with Octave.
McCullough, like Octave part of the newly set up Ulster College squad, edged a tight duel 6-4 6-3.
Windsor coach Przemek Stec said: "Annie produced the best tennis I have seen from her.
"Annie was very positive throughout the match, her confidence was high and she got the result she deserved.
"Hopefully she can build on this for the rest of the season," he added.
Next up for McCullough is another tough battle with number three seed Emily Beatty, while sister Caitlin plays her quarter-final today against Eimear Maher.
Bangor teenager O'Boyle got his day off to a good start when he defeated Will Millar 6-2 6-1 in the under-16s and then beat Matthew Duffy 6-0 6-4 in the under-18s.
O'Boyle's coach Paul Watt said: "Matt's serve has really come on, it's going to be a big weapon and he has developed physically which helps too.
"I think he has shown that this season is going to be very exciting for him."
Fellow Bangor man Chris Cree also had two wins, defeating Joe Heatly 6-4 6-3 and Matthew Robinson in an entertaining clash 6-4 6-2, both at under-16.
Boat Club's Laura Reid impressed with a 6-0 6-1 victory over Aiobhinn Kelly of CIYMS, while Windsor's Jakob Robb also had two victories, defeating Matthew McMullan 7-5 6-1 and Jordan McKeown 6-3 6-1.