The Similac nipple is a bit smaller than other nipples i've used, so for us it was more convenient when baby was smaller. But there is no functional difference from other nipples.
The rubber part stayed firmer longer than our Enfamil nipples.
The plastic ring detaches from the nipple. It can be sanitized by boiling in water for a few minutes.
I didn't like that the ring colour is white, it's a bit difficult to see when washing it in soapy water as it's the same colour as the soap foam.
We got these as samples with other Similac products.