These Tiemco bobbins are extra smooth ceramic, so as not to cut your thread. Not only are they the most reliably smooth, they're incredibly durable. As far as straight or curved goes, that's mostly aesthetic opinion.
Only 3 stars because of price. It is a nice bobbin, wraps well and smooth and no thread damage. But the price, I can get 2 Dr. bobbins for this price and they do just fine for what I need. Was this review helpful? (0) Yes (0) No