Are there Size options?

Hi, I am early 50s and having a double mastectomy in a couple weeks. I was lucky enough to have been picked up in early stage screening and lumpectomy was successful . I did not need chemo and just before I was due to start radiation my gene panel blood test came back that I have a brca mutation so on advice I am going with a double mastectomy and implant reconstruction. Decision was made fairly quickly as still active treatment and bypassing radiation. I never really asked about size and shape of implant, or maybe I just indicated same size is fine. Do you choose size? I’m in the public system and have my pre op appointment next week. Is this when it is discussed? I’m currently a saggy C and was curious if I have options…