Microsoft has cut $100 off the price of the Surface Pro 4’s dock, the day after Apple unveiled a Surface Pro competitor. The Surface Dock is available for $99.99 in a 24-hour Tuesday sale, but only when bought with a Surface Pro 4, a 12.3-inch tablet that starts at $899.

The steep discount follows Monday’s 9.7-inch iPad Pro unveiling, a tablet starting at $599 that Apple is targeting at Windows PC users running an older computer. The company cited a statistic that said over 600 million PCs in use are more than five years old. That’s a big market, and one that both Apple and Microsoft will be aiming to capture to boost sales figures for their respective platforms.

The dock, which works with the Pro 4, Pro 3 and Surface Book, plugs into the tablet and adds several more connectivity options. When plugged in with one cable, the dock adds four USB 3.0 ports, gigabit Ethernet, audio out and two mini DisplayPort connectors. When plugged in, the dock also charges the Surface.

Apple unveiled a similar accessory for its iPad Pro yesterday, albeit with far less connectors. The $39 Lightning to USB 3 camera connector can charge the iPad while adding a full size USB port to the device, something missing from the tablet itself.

Both devices also support a magnetic keyboard attachment, which can transform the device into more of a laptop replacement than before, as well as an optional stylus accessory that can turn the tablet into a better note-taking device than a traditional laptop.

Microsoft needs to fight hard against Apple if it wants to maintain its relevance as a key player in the consumer tech industry. Although Windows accounts for 90.45 percent of global desktop operating system market share, according to Netmarketshare, on the mobile side the picture is less rosy. There, iOS (which the iPad runs) and Android command over 90 percent of the market, with Windows Phone trailing on just 2.57 percent.