The 4 inch display is a recent addition to the company’s line of Raspberry Pi-related products. Pimoroni also also makes a 5.7 inch model that sells for £90 (~$108) and up, but it’s also out ...

The Raspberry Pi 400 is the brains of the operation, while the touch screen LCD provides the display. You’ll also need a keyboard, mouse, and power supply for the Raspberry Pi 400.” ...

You could argue that the project to add a round screen to a Raspberry Pi from [YamS1] isn’t strictly necessary. After all, you could use a square display with a mask around it, giving up some… ...

All Touchsy models feature 3.2 inch LCD displays attached to a small board that with connectors for different types of single-board computers, plus a few extra features like buttons or a buzzer.

You can use it with anything, not just a Raspberry Pi. I use my own on my server rack right now with my 16 port KVM, but I've used it for a ton of other projects too.