I believe she has (had?) double lumen implants. One side was replaced with 2 implants when she had a car accident. She was supposed to get the same double lumen to replace the broken one but there was an issue with the new one. She said that she found out after she woke up they had stacked 2 implants instead and she was upset by that. If you look at photos/videos post 1995 you might be able to see a difference.
One correction is that, from the info I have seen, the double lumen had an outer shell of silicone with an inner one of saline so that the implant could be increase in size. Since silicone implants come pre-filled they cannot be changed during or after surgery. The outer silicone shell would provide a better look/feel while still being able to increase the size after implantation but before the surgery is complete. Not sure if the size can be changed post-surgery like expanders but I think another surgery would be required to access the port of the implant.
From what I have seen there are different models of double lumen implants. Double lumen just means there is two (or more) shells in the implant, the outer one and another shell filled with the same or different fluid. There is one called the Ideal Implant that uses multiple shells but only saline as a fill.
Whatever implants SaRenna had they gave her, in my opinion, the best looking of the over-1000cc implants, with Tiffany Towers and Wendy Whoppers close behind. I really wish girls could get huge boobs that look like that today. But I don't think that is possible with over-filled 800cc shells or tissue expanders that doctors use these days. The closest I have seen recent is Billi Bardot but not sure what style implants she has.
We really need implant shells rated to 2000cc and up to be available to women who want to go to that size. Doctors used to be able to order pretty much any size they, and the patient, wanted. The government should not be able to dictate what size a woman can get.