Measure the diameter of your nipple!! The default spectra pump comes in 28mm breast flange, the full set is available from shopee https://shopee.sg/product/242594539/7732031072?smtt=0.0.9
if it comes with the old accessories, u try first loh, if too small u buy bigger size, if too big u buy smaller size
Nipple size you can Google online have alot of guidelines
Need to measure
C nipple size