anyone used a Yongnuo YN-2.0X III PRO 2xTeleconverter

[graycbr]

hi
Just seen these a lot cheaper than the canon ..
Your thoughts or has anyone brought one & got some feedback ?
Here's the specs
Features:
The YN-2.0X III is the updated version of YN2.0XII.
Allows focal length of the Canon EF increase to two times.
Ultrahigh refractive index glass coating have raised the level of the tele-converter.
The redesign of the upgraded electronic aspect make the auto-focusing function of tele-converter able to adapt to more lens, such as the EF70-200MM F/2.8 L IS II, the EF70-200MM F/2.8 L IS II USM and most of the lens can achieve automatic focusing.
Suit for Below EF EOS Camera Lens:
EF 135MM F/2L USM
EF 200MM F/2 L IS USM
EF 200MM F/2.8 L II USM
EF 200MM F/1.8 L USM
EF 200MM F/2 L IS USM
EF 300MM F/2.8L IS USM
EF 300MM F/2.8L USM
EF 300MM F/4 L IS USM
EF 300MM F/4 L USM
EF 400MM F/2.8 L IS II USM
EF 400MM F/2.8 L IS IS USM
EF 400MM F/2.8 L IS USM
EF 400MM F/4L DO IS USM
EF 400MM F/5.6 L USM
EF 500MM F/4 L IS USM
EF 500MM F/4.5 L USM
EF 600MM F/4L USM
EF 600MM F/4L IS USM
EF 800MM F/5.6L IS USM
EF 100-400MM F/4.5-5.6L IS USM
EF 70-200MM F/2.8L IS USM
EF 70-200MM F/2.8L IS II USM
EF 70-200MM F/2.8L USM
EF 70-200MM F/4L IS USM
EF 70-200MM F/4L USM
EF 300MM F/2.8L IS II USM
EF 400MM F/2.8L IS II USM
EF 500MM F/4L IS II USM
EF 600MM F/4L IS II USM
EF 1200MM F/5.6L IS II USM
And you can use it with below cameras in Automatic Focus function:
for Canon 5D, 5DII, 5DIII, 6D, 7D, 10D, 20D, 30D, 50D, 350D, 400D, 450D, 500D, 550D, 600D, 600Da, 650D, 1000D, 1100D.

NOTE:
1, The shooting environment, resolution and the brightness should be ideal.
2, The AF Point should be adopted the free selecting focus mode.
3, The Canon cameras outside the list have not been tested. In generally, if the camera focus system is advanced, it can realize automatic focus.
4, When Teleconverter EF 2X is attached , the lens maximum aperture will be smaller by 2 stop . In the above two case, the camera will compensate the exposure automatically.

Specification:
The Magnification: 2 times
Coating: multi coating
Lens composition: 9 elements in 5 groups
Item size: 7.2 * 7.3cm / 2.8 * 2.9in(D * H)
Item weight: 348g / 12.3oz
Package size: 13 * 9.5 * 9cm / 5.1 * 3.7 * 3.5in
Package weight: 439g / 15.5oz

Package List: D1698
1 * Teleconverter Extender
2 * Protective Covers
1 * Bag
1 * User Manual(Chinese & English)