# ProtoArc EM04 — Wireless Ergonomic Thumb Trackball Mouse > ProtoArc EM04 summary. A thumb-operated trackball that moves the cursor without sliding the body. Tags: mouse, protoarc, em04, trackball, ergonomic, wireless Source: https://www.amazon.co.jp/dp/B0CRQWQRMT Article page: https://web-autoai.com/articles/protoarc-em04-wireless-ergonomic-thumb-trackball-mouse?lang=en Prices and ratings change over time — check the article page for the current values. --- ## Overview The ProtoArc EM04 is a wireless trackball mouse that moves the cursor with a thumb-operated ball rather than by sliding the body across a surface. That design makes it a practical pick for cramped desks where there is no room for a mouse pad, and for unstable spots like a sofa or a bed. The shell is shaped ergonomically so the wrist sits at a natural angle instead of twisting outward. It connects over both Bluetooth and a 2.4GHz wireless link, and a single unit can pair with up to three devices that you switch between with a button on the underside. The left and right clicks use a quiet mechanism, which suits shared rooms and late-night work. Sensitivity steps through five DPI levels — 200, 400, 800, 1200 and 1600 — and the built-in 450mAh battery is rated for up to 70 hours of continuous use per full charge. Charging goes through USB-C, so there are no disposable batteries to buy. The body measures roughly 135 mm long by 100 mm wide and weighs about 118 g. ProtoArc notes that it is not intended for smaller hands, specifically those measuring under 17.5cm from the lower palm crease to the tip of the middle finger, which places it in the medium-to-large hand category. ## Connectivity & Compatibility Two radios are on board: Bluetooth and 2.4GHz wireless. Up to three devices can be registered and swapped with the switch on the bottom of the mouse. The bundled USB receiver stows inside the body, which reduces the chance of losing it in a bag. Supported systems are Windows XP/7/8/10/11 and later, macOS 10.10 and later, iOS 13 and later, Android 4.3 and later, and Chrome OS. That means the same mouse can drive a desktop, a tablet and a phone. There are six buttons in total: left, right, back, forward and a DPI switch alongside the main clicks. The back and forward buttons do not work on macOS, and remapping buttons requires separate software. Tilt-based horizontal scrolling is not supported. Only the left and right clicks are quiet — the DPI and back/forward buttons produce normal click noise. ## Product Info The EM04 launched on August 4, 2025 and sits in the entry-level price band, which makes it an accessible first trackball. Rather than chasing premium features like extra buttons or tilt scrolling, it concentrates on thumb control, quiet clicking and three-device switching. The ball can be lifted out for cleaning, which matters because trackballs collect dust around the bearings. ## Best Use Cases * People working on a small desk, a train tray table or a sofa who have no room to sweep a mouse around — the cursor moves while the body stays put, so no mouse pad is needed, though competitive gamers who need fine aim should look elsewhere. * Remote workers and night owls who need to keep click noise down; the main clicks are quiet, but note that not every button is silenced. * Anyone juggling a PC, tablet and phone at once, since three devices can be paired and switched with one button — not a fit for precision work like photo retouching or CAD. ### Product Disclosure (Amazon) - Manufacturer: ProtoArc - Model: EM04 - ASIN: B0CRQWQRMT - Note: This article covers a manufacturer-made product based on Amazon listing details.