Just bought one for use on another computer in the office for the MX master 1 from the prime day sale which arrived today. seems like a good deal. its going for $15 at centrecom. and rrp is around $20-$25
Bluetooth 4.0: Applies the latest Bluetooth 4.0 with low energy (BLE) technology
Driver Free: Plug and Play for Win 8, Win 8.1 and Win 10
Nano-Sized: Ultra-small for convenient portability with reliable high performance
Supported Operating System: Supports Windows 10/8.1/8/7/XP
TP-Link - World's No. 1 Provider of WLAN Products within last 10 years. Leading Support- Industry leading 3-year warranty and 24/7 technical support
Yes it's Bluetooth 4 but I have bought 4 of these now for older PCs and they work faultlessly for Bluetooth headphones.