The Ex-Tree extension for the Tree-Mate-O is for trees with larger root balls (20”-29”), multi-stemmed trees, forked trees, or other trees needing an extension to support straight healthy growth. Just snap the Ex-Tree extension onto the Tree-Mate-O, use the side tabs and the EPDM rubber bands for support. The EX-Tree extension is suggested for use on trees up to 2.5” in diameter. Sold separately from the Tree-Mate-O.