[USB-A (2.0)] Mini USB Bluetooth® 4.0 Adapter is a fantastic product! Better working range than other Bluetooth receivers/transmitters. Works great with Sony MDR-10R after checking ALL of the configuration for USBBT1EDR4. You MUST install ONLY the last version of the CSR Harmony software; if you have an older version installed, you MUST uninstall the older version first. The new version unfortunately does not include drivers for all of the older transmitters and you can't have more than one version installed at the same time.
I highly recommend this product.

[4.0 + EDR] I wanted a Bluetooth adapter to allow the connection of a keyboard and mouse to my desktop. Works great with Windows 7.

[USB-A (2.0)] I bought Waves NX Head Tracker to use it with Logic Pro X in a Mac Pro Mid 2010 OS El Capitan and Bluetooth 2.1 I needed Bluetooth 4.0, so I bought this StarTech adapter. Plugged into my computer, but it was not recognized as BT 4.0. Then I downloaded Hardware_IO_Tools_for_Xcode_7.3.dmg, and installed Bluetooth Explorer in the Applications folder. Opened it, Tools menu and choose HCI Controller Selector, I clicked at the arrows and selected Broadcom Corp and clicked Activate. Done My computer recognized the StarTech adapter as Bluetooth 4, and I was able to use my excellent Waves NX Head Tracker.

[8DPSK, GFSK] I have a 2019 Mac Mini that always had weak bluetooth reception for my mouse & keyboard. I bought is as "refurbished" and this is probably why someone returned it in the first place. Anyway, to get to the point, I ordered 4 solutions from Amazon and this Mini USB adaptor was the only device that fixed my problem. I'm using that same keyboard & mouse to type this review. Even though there wer no instructions on the device, I did plug it in, turn off the Bluetooth reception in the Mac Settings, used a wired mouse to turn Bluetooth back on again and it has worked perfectly for the past 3 weeks. My frustration has ended!!! Thanks StarTech!

[0.22 lb] I tried this adapter on two Windows 10 laptops. Windows did not find and install a driver automatically on either one, but I came to this site, downloaded the driver package, and was in business on both machines in a few minutes.

[4.0 + EDR] this works on older CPU without bluetooth AI

[USB-A (2.0)] This is a very good product. The driver software is very comprehensive and reliable.
A big advantage is that it supports wake up from sleep function for keyboard/mouse devices. This is the first adaptor I have come across which includes this function.
So far have not found any disadvantages or problems.

[0.22 lb] this works to connect my PC with bluetooth headset

[USB-A (2.0)] I have an iMac from late 2009 and by bluetooth was not totally compatible with the Magic Track Pad 2. Before ordering the trackpad I researched on the internet, spoke to people at Apple and B&H. What I got was varying opinions. What I concluded was that I should spend the extra money. When they arrived I paired by trackpad to my iMac without the adapter. It worked initially. But when the iMac went to sleep, the pairing was lost. I hooked up the adapter and since then the trackpad and iMac are happily paired. One last comment. Since I bought from B&H and live out of New York State, there was no sales tax. That combined with the lower price for the trackpad at B&H, I saved money versus driving to the closet Apple Store. Thank you B&H!

[USB-A (2.0)] I bought the Bose QC35 wireless headphones and could not connect to my older Mac Pro. Turns out the Bose QC35 required Bluetooth 4.x, and the Mac Pro has Bluetooth 2.1. So I bought this adapter and it worked like a charm. I can now connect to my iPhone 6S and switch to the Mac Pro easily.