This little thing is adorable! It's only about 2 inches long, trust me it looks small in the pictures but it's even smaller than you're imagining. I took a picture with it next to a Nintendo Switch Joycon and a stick of Burt's Bees lip balm to show just how tiny this controller is. I can easily hold it in the palm of my hand and push all the buttons with my thumb, so I can even play some games with one hand (this is useful when you have three dogs who all demand lots of attention and scratches lol).
I bought this for use with a retro game emulation handheld (the Retroid Pocket 3, to be precise) and it's great for retro games that don't require thumbstick controls. It was really easy to connect via Bluetooth, and now that it's paired with my handheld, all I have to do is turn the controller on and it automatically reconnects. Sometimes if I turn on the controller while I'm in the middle of a game, it won't register any inputs from this controller or from my handheld, but when that happens all I have to do is open the main menu then reopen the app and it works again. I'm pretty sure that's an issue with the Retroarch app and not with this controller, just figured it's worth mentioning.
This controller seems well built and feels like it will be durable, though I haven't had mine very long to test that. This is a great option if you want a tiny controller for retro gaming, and it would also be a great cheap alternative to joycon if you have kids playing Mario Kart or something on Switch that doesn't require a full pro controller layout.