I have researched this line of clothing on several different websites and have found that the sizes range from Petite to 3 Generous. Petite is size 4-6, small 8-10, medium 12-14, large 14-16, G1 18-20, G2 22-24, & G3 26-28.
Sizes for Flax clothing run from Small to generous 3, Which is most likely a size 30, which should be a plus size 4x i believe. I have seen a few pieces also, they seem to be a very nice clothing line.