If you are going to get one go with the Kenko Pro 300 series. More expensive
but the best on the market for general purpose. Don't expect very good
results though the Sigma lens is not going to produce sharp pictures.

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"PeterH" reply to wrote in message
news
Do you recommend a Tamron 2x converter for a Canon 300D with Sigma 70-300
APO macro super zoom lens?

Any other recommendations?

regards

PeterH