While many laptops have Bluetooth built-in, there are still many that do not. Bluetooth is extremely useful for the laptop because it allows the use of wireless peripherals such as a mouse or keyboard. Even more useful though is the ability to tether a laptop
to a mobile phone. This can allow a laptop to access the internet when Wi-Fi or wired networks are not available. The IOGEAR GBU521 allows any laptop that has an available USB 2.0 port to support Bluetooth devices including version 4.0 devices. It's relatively small size is also great because it doesn't stick out too far from the laptop where one might risk bumping it and damaging the adapter or worse, the laptop. Priced between $10 and $20.