So useful saving time recounting stitches cast on plus lots more.
These are SOFT rings. They are great when you first cast on. I suggest you use one on after every 20th stitch. As you knit you can click the ring from the left hand to the right hand needle.
You can remove them after a few rows then later use them to indicate increases across your row. Make sure you buy SOFT rings for these purposes.
HARD rings look the same but you cannot flick them. I use hard rings to indicate to my fingers while knitting the position of a pattern change such as a line of cable. One ring each end of the pattern panel.
I have also used the rings on home made Christmas tree ornaments to tie loops too.
I would not be without them.