The pants are knit construction; the ribbed option is specifically described as jersey knit ribbed fabric.
Follow the garment care label. Listings state the pants can be machine washed and tumble dried, and descriptions note the fabrics generally wash well.
Descriptions state the pants "wash well" and note they do not excessively shrink or lose color, indicating color and shape are expected to hold up with normal washing.
Many listings show sizes from XS to 3X (8 sizes available), while the solid ribbed option lists sizes from S to 3X (7 sizes available).