TL
R actual question is at the bottom.
I would love to use prewound bobbins, if I could figure out how the prewound people's system fits into my world. Really, you people are to blame for this. No, seriously, you are. Right here on this forum, too. Life was so simple when I was married to my Necchi Supernova Ultra Mark II. (Well, except for the length of the name, I will concede that.) Only one kind of bobbin to buy, none even looked close to it, and I turned my nose up at Singers and snubbed their flimsy little funky plastic bobbins. Even the metal ones- they clearly hold less thread, why would I even bother to lower my standards and down grade? It's unAmerican- we only go up, and there is clearly no up from my beloved Necchi. I was the poster Necchi Girl.
Then, somehow, you sang your siren song and lured me over to the dark side. (Although in my Necchi's left-handed defense, there was a transformer blowout involved here.) But, at least I had some scruples left. I mean who in their right mind would sew on a slant shank machine? Seriously, engineering, power transfer, physics, blah, blah, no thanks! Another clearly lower standard. There must be some pheromone in PB Blaster (it does have a strange smell, right?) because here I sit at my now everday machine, and it's a 401a. Everything I loathe(d.) A slant shank, weird model 22 bobbin machine.
So, I need a little support here, people. I need a translation device from my old reality to my new one. We have model 15 and style 22 bobbins. Prewounds come in 15s and L and M. (And I have a random Clark's paper sided bobbin marked Style "H" size 60/36 which is too big for the 401a. I checked.) So, which matches the style 22, the L? It's unbelievable that the bobbin sellers do not seem to have this information anywhere on their sites.