Write a question about the article

I have a size 6 pink pair of Abercrombie jeans ! I ' m amazed I can even fit into them but I can ! and I also got a size 10 pair of Donatos jeans which are blue with tan trim down the legs and man they are SO TIGHT but I can still wear them but go figure the difference in sizes and brands . I usually take a 7 or a 9 in pants anyways .
What may be the reason they are so tight ?