“I have a 1st Generation Raspberry Pi B with an original low-power PSU, running an old Raspbian Wheezy. Because of the old pi, low power and old software version, I've had problems with other USB WIFI adaptors. This one worked out of the box with only a tweak to the /etc/network/interfaces to get it running.
Excellent product and I intend to buy another.
If it helps, my /etc/network/interface file is
iface lo inet loopback
iface eth0 inet dhcp
iface wlan0 inet dhcp
NB You'll also need to set up the wpa_supplicant file.”