module that allows to define minimum quantity of products for selected customer groups. Customers will have to add required product quantity to go throught order process. One additional great feature in this module is an option to accept only defined quantities of product. This means that with this module you can sell some products in packs only (you can enable this feature only for selected produts). For example, with this addon module will accept only defined quantities like:
Each product can have own unique value of this restriction. In addition to this, you can define minimum quantity for selected combinations of product. Each group can have own unique minimum value too.
more details about module is available here:
Minimum product quantity by customer + accept multiplied quantity only