Just FYI, I purchased an Extreme Tools 41 inch 11-drawer rolling cabinet a year ago and was satisfied with the purchase until I rolled the unit into my garage, which has a slight height difference at the threshold between the garage slab and the driveway. Even though the toolbox wasn't fully loaded (much less than each drawer is rated for as specified on their website), rolling over the 1/4" garage lip caused the sheet metal underneath the cabinet to buckle on the seam, right where the caster is bolted to. This buckling causes the two cabinets to lean about 10 degrees, and i'm unable to roll the cabinet safely now. The other caster is starting to bend as well due to the mismatched height of the two back casters.
After calling the company and submitting a warranty claim, the company representative states that "the owner of the company has determined that this is not a factory defect." and have stopped responding to communication. So I'm out over a thousand dollars because Extreme Tools will not honor their own warranty. Buyer beware, these Chinese made toolboxes look nice but do not hold their rated weight and the US marketing company that rebrands them has no intention of standing behind their product.
https://imgur.com/a/LCsHI