Suekaphin Nursing Bra 5pack Wireless V Neck Maternity Nursing Bra Bralette Low Cut Sleeping Breastfeeding with Extenders

I'm not sure if I am a large or extra large in this brand. My underbust is 34, bust is 39, underarm is 37. What size would fit me best?

I ordered a pack of bras and one bra while also marked a medium is definitely larger than the rest of the bras. Can I exchange it or what should I do?

Do all the straps have a sheen? (On both the heathered and non heathered colored ones?

I’m usually a 38a/b before pregnancy, would a large or x-large fit better?