What materials is it made of?

All fabrics/fill are 100% polyester. Shell: 90GSM microfiber, brushed both sides. Fill: 240GSM down alternative, no down/feathers. Sheets/pillowcases: microfiber. OEKO-TEX STANDARD 100 certified; TESTEX certificate No. SHHO 073426.

Does it include pillow shams? What is the difference from the pillowcases?

Queen and larger sets include 2 envelope pillowcases for sleeping and 2 decorative shams, without pillow inserts. Inner flaps help keep pillows inside. Twin/Twin XL are 5-piece sets with 1 pillowcase and 1 sham.

Is this machine washable?

Yes — Machine wash cold on gentle; tumble dry low; do not bleach. Wash the comforter separately from sheets to avoid overloading. Low-heat drying also helps restore loft after vacuum compression.

What sizes are the pillowcases and pillow shams?

Queen: pillowcases 20"×30"; shams 20"×26" + 2" flange. King/Cal King/Oversized King: pillowcases 20"×40"; shams 20"×36" + 2" flange. Sizes vary by set size. Pillow inserts are not included.

Will the fitted sheet stay on my 15-inch mattress?

No — the fitted sheet has a 14" deep pocket and fits mattresses up to 14 inches. On a 15-inch mattress the elastic will not hold and the corners will slip. If your mattress is 15 inches or deeper, choose a set with a deeper pocket.