If you need high altitude training for GMAT quant, then try Gmat club tests

What’s good
1. Great interface: GC test has outstanding Interfaced of Test this is almost similar to that of GmatPrep CAT. Few more awesome features
• While reviewing your incorrect question, it can let you attempt the question again rather than displaying the answer
• It can let you make a note against each question.
• Review stats, mark a guess
2. Quality of question: Questions are amazing. While some of questions exactly mimic the Official questions, most of the questions are fresh and one can be assured that each question tests you mostly relevant concepts.
It provides training which analogous to high altitude training to an athlete
Explanations are crisps and short

What could be better:
I am not sure how the algorithm works. Final raw score are not sometime consistent.
Scope pf improvement for verbal questions

In summary, if one is shooting towards Q51, these tests are must. You can’t afford to miss them.