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 speed of 40 km / h. As a mechanic and welder I've seen many poor quality parts but this might be one of the worst. My advice is if you want cheap bearings, find another set and forget about these.