Used Sony FE 2x Teleconverter

Having this on my 70-200mm, the image quality holds up well considering it's a 2x extender. The lock mechanism feels solid, and autofocus is still snappy in good light.

Decided to mount this on my 135mm and the extra reach is fantastic for birding; the build feels just as solid as my new Sony gear. Used condition was spotless and the glass is perfectly clear.

Doubling my 70-200mm's reach to 400mm has been a game changer for birding, and the used unit I got locks focus just as fast as my native glass. A bit of a fingerprint smudge on the barrel, but the optics are crystal clear and worth every penny.