From my 3 year old down to my 8 month old these are still a favorite. We got these originally attached to a fisher price portable swing when my oldest was born. The link-a-doos outlived the swing by far.
Link-a-doos are nice bright colored rings that are teethable plastic, each with a different design, some have flower tips, cute faces or just plain rings. Very easy to keep clean and disinfected.
They come in really handy to attach toys to a stroller, car seat, highchair, or just to the other link-a-doos. I use them to attach my son's crinkle book with mirror to his swing, so I'm not running every two minutes to pick up the book from the floor. We also use them to attach toy to the car seat so when we are out we don't have to worry about toys landing on the floor and get dirty and running to find water to clean them so baby can play with them again.
My two year old attaches them all together and drags them behind her pretending to be walking a dog.
They come 20 per pack, my suggestion is if you have more then one baby or toddler get more then one pack.