So I made a stupid mistake and bought a Sigma 1.4x Teleconverter (EX DG model) from eBay. I was looking for Canon EF mount and somehow I managed to buy a Sigma mount. I double checked the listing and nothing in the listing states Canon so it's totally my fault (impulse buy after a long day at work, probably couldn't read straight if I tried).
In any case, I am super confused now because the teleconverter accepts Canon lenses but mounts on Sigma. So picture my confusion when I was able to mount my Sigma 70-200 OS (EF mount) on it and then went "WTF!!!" when I tried to mount the teleconverter on my 70D.
Has anyone run into this before?