I asked my wife to order these bearings to replace the ones that failed in a small kart but after about 10 rides of about 10 minutes each they fell out a part. Understand, those were the front tires, so they didn't put much weight on them. They are also a double bearing wheel so the stress on each bearing should be even less which basically means a regular set of cheap bearings should work just fine. However, these bearings are apparently so bad that they can even handle a small kart with a top