As Microsoft has done in the past, it has created a fork in its Windows Insider program as it looks ahead to its next major upgrade. Insiders who want to stay on the current path can do so and will continue to receive new Redstone 4 builds in both the Fast and Slow rings. Likewise, Insiders who want to test out the next major update to Windows

Source: Hot Hardware – Microsoft Brings Ultimate Performance Mode To Windows 10, Releases Redstone 5 Test Builds