I have the now defunct 21mm bar made by Progress Tech which was distributed by South County Autosports. This is different the the BAT bar.
Bar is supposedly strengthened to that of a 22mm bar. My opinion, I don't think this stresses the stock brackets or bracket mounting plate as much as the Aussie hollow 24mm bar does. Yes the 24mm bar weighs less. I just uninstalled a Aussie bar from a friends car last week, he was trading the car in and it weighs less than the stock 18mm bar.
To date both bars have ripped the mounting plates off the subframe from a few cars on this site but I have only heard one case of the 21/22mm bar doing it. I drive my card hard around corners and the worst problem I have encountered is bent brackets. I upgraded to some 21mm ProThane bushings/Type A brackets and for over a month I have had no issues.
Its all a matter of opinion, I think the 21mm bar is the way to go for ease of install and lack of bracket/subframe problems others will say Aussie hollow 24mm bar.
Both are good and improve the handling.
