I think the ones with the "S" curve have the split for threading on the side which might catch on both the fabric and the batting. Those are the type that are being advertised on TV right now. I'm not buying those... but, the older type that has the slit for threading at the back end of the needle seem to work great for burying threads. The ones I've used also come unthreaded easily too so I don't use them to actually quilt.