I use a sizing system of: XS, S, M, L, XL, XXL based on the European standard sizing. All pieces are true to size. Email me with your everyday bra size and your everyday panty size if you are unsure what size you would be and i will assist you with correct sizing.
Between two sizes? Your right style and size will also depend on how you want to wear them – showing more skin, or less; sunbathing or surfing. I would recommend going for a size smaller if you are between two sizes since the fabric is super elastic and formes after your body.
Most designs is designed with adjustable opptions to really get the perfect fit.