South Africa's Lloyd Harris is into the quarter-finals of the Halle Open after he beat Lukas Lacko of Slovakia in straight sets.
Harris won 6-3, 7-6 (10/8) and was made to work hard in the second set to secure victory.
The big serving South African managed 11 aces but struggled with his first serve and only managed a 53% service percentage.
However, when his first serve did let him down, he managed to win 69% of the points on his second serve.
He will now face either Phillip Kohlschreiber (Germany) or Andrey Rublev (Russia).