If you hover over the "Available sizes" a tap will appear and provide you with the correct numeric sizing. The fit on the Terramar Woolskins Merino Wool Bottoms is going to be a trim fit.
Yes, they are low rise! I didn't like the fit and am exchanging the M for size L, hoping that will make the rise more comfortable. I want to wear these as around-the-house pjs and don't want them to be low cut. The fabric is gorgeous quality -- very smooth & silky.