They are not adaptive; they a set of carefully selected 37 questions for Quant and 41 for verbal.
The 25th Quant and 6th Verbal tests are free so you can test drive them. We also make them available on holidays free of charge (Memorial day is the closest one at this point).
You can also browse the GMAT Club Tests
forum to see some of the question samples: gmat-club-tests-59/
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