Fujifilm XF 100–400mm f/4.5–5.6 R LM OIS WR Lens

$100 off is a terrible deal for the tradeoff of possibly losing warranty

Thank you for the reply , this is very helpful.

I used it on the X-Pro2. Autofocus speed was good but not great. The two most difficult scenarios I used it in were with the hummingbirds and with monarch butterflies - small targets that don't hold still in the closer end of the focus range. In those situations, I found the autofocus usable with occasional frustrations. On the other hand it worked great at the zoo where the animals weren't typically moving so fast. I would want more practice using the Fuji AF settings and the lens to feel more confident in shooting these sort of subjects with better accuracy, but it was never bad enough to sour the experience.