AnonymouseThese are flat on the bottom which means that you can leave them on your project until you are right up close to the needle on your sewing machine. They also have measurements on the clear underside which are useful when measuring hems, etc. Also they are much shorter, which means they are less likely to catch on something and fall off or shift. They are great for bindings but even better for bags or other projects where you are sewing lots of thick layers together.
They don't seem like big deal until you try them but they are awesome!