The "2021" designation usually indicates the model year or the specific software revision for that year's production line.
Once I have a little more context, I can hunt down the specific content or summarize the key points for you! sp furo 13wmv 2021
The SP Furo offers the best bass-to-price ratio among 12–13” marine coaxials. It outperforms 10” models in low-end punch but doesn’t require the massive amplification of the Wet Sounds REV 12. The "2021" designation usually indicates the model year