Plate carriers are sized to the plates, not the person. The size associated with various plate carriers usually refers to the size of the plate bags. Our AC1 is no different as it has the same cummerbund and shoulder strap adjustments across all sizes, the only difference between sizes being the plate bags.
Please refer to our sizing guide on the AC1 product page to determine which size you'll need for the plates you own or plan to purchase.
You will need to determine your plate size first and then grab the corresponding plate carrier size. Not sure what size plate you need? Check out Hesco's Hard Armor Fitting Guide.
Shoot us a message at firstname.lastname@example.org if you still have questions, and we'll be happy to help!