I started down the silk rabbit hole with a silk pillow case. I wasn't sure I would like it, but wow! The material felt so good on my face at night and it always feels cool to the touch. So I figured I would try silk pajamas.
I love them! The material is so wonderful. It is silky and very light. If you are traveling, they are great because they are so light they take up almost no space.
I wear a size 8 and needed a size M. I am 5'2 and 145 lbs. Silk has no give at all, so you don't want to order too tight.
Make sure to buy a detergent that is made for silk. I machine wash in a garment bag and line dry. Silk dries very quickly.