mCat – Pronunciation: ’em-kat mCat Numbering System for Tennis Containers Each container has been assigned a number based upon the mCat (McCall Catalog) system that I developed. Numbers consist of four segments each part representing a specific constituent of the container it characterizes. 220.127.116.11 Manufacturer: (Spalding in this example). 18.104.22.168 Can ID: Each can has an ID number. Similar cans of different types and different number of balls may share the same ID. 22.214.171.124 Type: Denotes the container type (see page on type definitions) . 126.96.36.199 Number of balls the container was designed for. Lets say that you have some identical or very similar container designs that are of varying Types and ball capacities. You can assign the same basic mCat number while changing the Type and ball number segments to match the particular container. See the example presented below based on a Spalding Type 1 three ball container.