Hello Quiltngolfer
I bought my Janome 8900 about a year ago. From the same dealer I took home a package of bobbins I specified to use with this maschine. At home I discovered that those don't have the J on them, only those that came with the maschine. I use them anyway, I couldnt find a difference in weight, height, or material.
I love how she sews :-)
rainbowcat