Comparing A to L and other bobbins
I know some people use Style L bobbins in their machines when they can't find Style A bobbins (mainly in UK where Style A prewounds are difficult to find) beliveing that the only difference is the depth - which is what I thought.
But I came across an interesting document specifing exact sizes for comparison of bobbin Styles. http://thethreadexchange.com/downloads/the-thread-exchange_bobbin-style-guide.pdf
I though it interesting to see that Style L bobbins whilst shorter than Style A are actually about 2 tenths of a millimeter wider. I don't know how this would affect the stitch if using them in the 12000/15000 but a sewing machine is a precision machine so I would definitely only use Style A.
"Life may not be the party we hoped for, but while we're here we should dance". Anon