Unless if you are asking for what CRM's RingCentral integrates with? If this is the question i would recommend visiting https://www.ringcentral.com/apps/?q=crm for more information.
NetSuite CRM is a robust and powerful customer relationship management solution that provides companies of all sizes a complete 360-degree view of their customers in real-time. Users enjoy a continuous stream of information from all points and throughout their customer lifecycle