Grab a tape measure & check out the below before ordering. Note these are your measurements, not the garment's.
Bias cut garments have several inches of give, so don't worry if you don't match the measurements exactly, pick your closest match.
Corsets are designed to have a small opening at the back. This allows flexibility with sizing and also means you can lace up tighter or looser depending on how much cleavage and/or oxygen you desire.
Custom sizing is available for if you are outside of the size chart or have body proportions that vary significantly from the standard sizes. Also if you want an extra few inches of length on a skirt, etc.
For more information on custom sizing, email prior to ordering. Even if only minor adjustments are required, please email us to discuss prior to ordering otherwise we can not guarantee your request will be met. 
Some garments have a surcharge for custom sizing due to the additional work or materials involved.
Pristine's size range will be expanding as soon as it is affordable to do so. Size grading & sampling is a costly process and due to the limited finances of a new company with no financial backing, it's unfortunately not yet possible. Sorry about this.
If you need help measuring yourself, this is a great resource.