I'm not sure, the remnants of a factory frame is just a single stripe of black plastic on the bottom back panel. The tank has DIY euro bracing from at least 2 of its previous owners. One owner had it euro braced with a center only brace, the second owner modded it for an overflow, removed the center euro brace and had 6 returns drilled in the back glass with twin center braces added in like modern 72" tanks would have.. But I loathe euro bracing so I want to scrap the glass bracing for plastic molding. The inability to run HOB filters really annoys me. I'd rather have 6 aq110s than a sump, since those wont overflow an make my living room a river.