I ordered a medium Macom which is supposed to be right for a 34 back which I was pre op. Luckily I also bought a bra from Amazon which I took op day with me because after I had my 450cc implants that Macom was never going to fit. I have since exchanged it for a large which to be honest isn’t as comfortable as my Amazon one (which I’ve now ordered 3 of haha). I was 34a before and with slightly bigger implant so I would say you will need the same as me. Also other bits to buy are a sippy cup or some straws, ice packs gel ones are best, a hot water bottle for your back, peppermint and ginger teas for bloating, arnica tablets for bruising (I took these straight after the op for 7 days and had no bruising when I had the strapping off. The nurse thought I looked fab). Make sure you have button up or zip up and trackies for op day and the following few days.