The authors consider closed queueing networks which are useful for discrete-time models and extend the product-form networks in the literature in two ways: (a) different size batches of customers can depart from several queues simultaneously; (b) the rate at which batches are worked on has a more general form. The following three cases are under consideration: (1) Closed networks in which individual customers are labelled; (2) Closed networks in which individual customers are not distinguished; (3) Networks in which customers occupy labelled positions at each queue. For all these cases the product-form results are obtained.