There are three main types of IMS perforation that differ in the inter-axes of the holes; it is possible to modulate the extraction of coffee by varying the pitch of the array of holes. The characteristics that determine the specific model of a filter basket are: the border, the shape and the ridge (also called groove). A lot of planning and technical expertise goes into making these filter baskets and shower plates and shower screens by IMS.
All IMS products can be found here.
Free 
Service 
