Oh, my goodness! I have a Janome 7700 and use bobbins from WalMart! They look just like my Janome bobbins and work just like my Janome bobbins. I use the same bobbins, in both my Janome 7700 and my Brother CS6000i. I've never had even the slightest problem with them.
When I bought my machine, the LQS dealer assured me these less expensive bobbins were just fine . . . and he was right.
