The Logitech MX Master line has been called the “gold standard” productivity mouse for a decade, so when the MX Master 4 showed up everywhere at $120 (and yes, it’s the most expensive MX ever), I did what I always do: I dug past the headline features. In this video I break down what actually delivers day one—MagSpeed scrolling up to 1,000 lines per second, an 8,000 DPI Darkfield sensor that tracks on glass, 70-day battery life with fast charging, a tougher matte finish that doesn’t melt into gross soft-touch goo, USB‑C Logi Bolt, and clicks that are way quieter than the MX Master 3. Then I go after the feature you’re really paying for: the Actions Ring with haptic feedback. Logitech claims “up to 33% faster productivity” and 63% less mouse movement, but that number comes from a Logitech-commissioned study of 37 users. Also, the native Actions Ring integrations are thin at launch—Photoshop, Lightroom, and Zoom, with Premiere Pro “coming soon”—and everything else needs manual setup in Logi Options+ running constantly in the background. My verdict: if you’re on an MX Master 3 or older, it’s a legit upgrade. If you’re on a 3S and upgrading for Actions Ring hype, verify it actually supports your workflow before you light $120 on fire.