The Galaxy Expand Is based on a multi-slot 19 inch wide x 7" high (4U) x 10.25" depth chassis. There are a total of 11 slots to support a variety of Server and/or telephony interface cards. In addition, there is a slot for the Switch Fabric card, which is used for in-chassis communication by all the other pluggable cards. All other cards, including server and telephony interfaces cards are optional.