Maintain the Infoblox NT-MRI-500-100 platform under a defined one-year ISP L3+ maintenance term. This service applies to the named supported product rather than adding another appliance, interface, or software instance. It gives deployments using that platform a specific annual maintenance designation and service tier to associate with the installed system. The covered period is one year. NT-MAIN-MRI-500-100-S21 identifies the maintenance service associated with the NT-MRI-500-100 product. Select this service where the supported system matches that designation and the required maintenance level is ISP L3+. The SKU represents a service entitlement for the supported platform, with its scope centered on the stated product, annual duration, and named service tier. The key selection points are the supported product, covered period, and service level. Here, the supported product is NT-MRI-500-100, the service period is one year, and the tier is ISP L3+. Those characteristics distinguish this maintenance selection from service options that differ by duration, supported platform, or tier. It is a service item with no physical hardware component.