I have been looking at extending the maximum focal length on my 70-200mm f/4 with a Canon Tele Extender. 1.4x seems to be a sweet spot for that added focal length without taking too much of a hit on picture quality. I came across this auction on eBay. Seller has perfect feedback and there are 7 bids on the item already, don’t miss out on this great piece to complement your Canon zoom lens:
