Luxembourg's 34-year-old Gilles Muller and Croatia's 38-year-old Ivo Karlovic set up a final between two of the tour's veteran big servers at the Den Bosch grasscourt tournament.
Muller defeated Germany's second seed Alexander Zverev 7-6 (7-5) 6-2 in the first semi-final.
Karlovic then won an all-Croat contest with top seed Marin Cilic 7-6 (7-4) 5-7 7-6 (7-2) despite not having been able to once break serve against his younger compatriot to set up a Sunday showdown.
Muller, seeded four, used all his experience against an opponent 14 years younger in romping through the second set.
After a tight first set, it was a disappointing ending for Zverev, the current world No.10.
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Karlovic, the tallest player in the men's game at 2.11m, once again proved just how difficult he still is to beat on grass as he crashed down 29 aces against Cilic, in a serve-dominated marathon.
Cilic was the only player to earn a break of serve in the two hour 46 minute contest as he levelled the match at one set all but Karlovic, who also had a match point at 6-5 in the third, won both tiebreaks handily.
