The ones I purchased are on clear plastic bobbins and my Husqvarna Sapphire 870 does not indicate when the bobbin is low with them... nor does it with the blue Husq. bobbins from my Lily 540....I have to use the green Husq. bobbins for my machine to indicate when the bobbin is running low. I don't usually piece with the bobbins that are pre-filled I usually just use them if doing fancy stitching with a stabilizer behind them. The thread is definitely lighter maybe a 60 wt ??? and I usually piece with a 50 wt.