Paul, Thank you for the insights. Looking forward to read your written reviews on how TK9000 4U perform on your hand. 4U rackets, for my personal taste, has always been "less-durable/weaker" rackets compared to 3U version. Off the records, I once read (hope someday i could find the complete documentary video behind the scene of racket production) how these manufactures produce their rackets in bulk, which after QC, the "passed-the-test) ones would be marked as 3U (depending on their initial intended final weight), slightly less-heavier than expected would be marked 4U, while little-heavier than they expected would get the mark 2U (unless 2U weight is what they expected during planning phases). Of course this marking system by QC might not apply for rackets with 5U & 6U weights as they were produced intentionally light-weight. (you could always try to dry-weight 2-3 the same rackets of the same brand of the same marked 3U or 4U, and eventually the number weight won't always exactly the same). Just my 2-cent here.