To get an idea what the binder will feel like on: after you measured yourself, take a broad bandage and cut 12cm off. Now put it on over your breasts and fasten with a safety pin.
I make the binders in
X SMALL (76-81cm) - 30-33
SMALL (81 - 87 cm) - 33-40
MEDIUM (87 - 92cm) - 36-43
LARGE (97 - 102 cm) - 40-50
EXTRA LARGE (97 - 102 cm)- 50-58
2XL (102-107) - 50+
Please measure yourself under-arm over the nipples to get the exact circumference size. There is a play of 5cm for each size the same as when you buy clothes in a shop. I make the binder 12cm smaller than your circumference in order to give you a snug fit. See side note.
You don't want this binder so tight that it cuts into you skin - it should fit comfortably.
PLEASE NOTE: If you go to the gym regularly and developed big arm- and shoulder muscles, but still have a small chest circumference, a small will not fit you - you will burst all the seams forcing it over your shoulders. If you regularly take Testosterone your breasts would have shrunk. These chest binders will not fit you, because a Large going over your shoulders, will have the same circumference than your chest and will therefore not suppress your breast size.
I had come-backs where Smalls complain it is too loose. Remember - if your breast size fell between 81 and 87cm, you are not going to get X Small over your head and shoulders. Then you have to order the one that opens at the side.
If you take a big size, please remember that the non-stretchable front panel will suppress your breasts, but it will hang losely under the breasts. In that case (if you are big chested) it is better to take the longer version that you can tuck into your pants.