I also bought my bobbins off ebay. I bought 50 for around $3. I got them a couple of years ago and use them in my embroidery and quilting machines. I think I've had only 2 break so I'd buy again in a heartbeat.

The set of bobbins on Amazon labeled "for Kenmore" which ClairVoyant pointed out to me arrived today. They are just fine. They are all round and even and they all fit on my bobbin winder.

I think the set of 20 will take a while to arrive. I still doubt they will be very good but at least Amazon offers a good guarantee.

Update - the set of 20 bobbins from China/Amazon arrived. They did not seem bad. I discarded one, it was off kilter. The other 19 look fine. I think the previous Amazon purchase (not from China) seemed a tad better in quality. Between the 2 orders, I think I have enough bobbins for a while. Thanks to all who advised.