This is module that will give you possibility to define value of maximum product quantity that customer can add to cart (can't order more). If customer will try to add more quantity of product to cart - module will block possibility to do that and customer will see nice modal popup with information about that.
And what's the most important: with this PrestaShop addon you can define different quantities for each product in your catalog, you can define different quantities for selected groups of customers!
This means that each product can have different settings for each customer group.
more informations about this module you can read on official module website:
maximum quantity of product that customer can order