They are great of you can get then to chew on that rather than anything but the ones you can freeze sounds great I just had a normal ring

I used the ones you speak of too. But some kids prefer a hard surface to chew on without the addition of the cold factor

I used the ones you mentioned without issue

I have to be alarmist but it depends what the liquid is whether or not they are safe. Strangely not all babies like them frozen or very cold. We had a solid plastic one which we used for 3 children. It is over 30 years old now, has been well chewed and surprisingly not showing much wear. I was used last year for the 3rd one.