CRM Client Access Licenses (CALs) are required for each device or user that accesses the features and services of Microsoft Dynamics CRM Professional or Enterprise. Device CALs are likely to be more cost-effective than User CALs if there are multiple users per device (for example, a call center or an airport kiosk). This CAL provides write only access functionality, and may only be purchased to supplement a limited CAL with write access capability. Microsoft Software Assurance is a maintenance offer that helps your organization get the most from Microsoft software through a broad range of benefits from deployment planning and staff training to product support and software upgrades.