They are Gooooood

GmatClub offers 25 Quants Mocks/Cats and 9 verbal Mocks/Cats. Quant Cats offered by GMAT club are good. Their questions will make you scratch your head to solve it. They focus on all three levels that are basic medium and high, but above that they test you from all the possible angles and that what help. They have got good trick questions. As far as the Verbal section is concerned it is not as great as the Quant section but good. As far as, the scoring algorithm is concerned. Don't rely on it, because the only mock that can give you closest score to actual GMAT is official mocks. But for practice and preparation quant mocks are worth it.