What are typical twin box spring dimensions?

Box spring has following sizes: Twin, Twin XL, Full,  Queen,  King

Twin:  75*38*6

Twin xl: 80*38*6

Full: 75*54*6

Queen: 80*60*6

King: 80*76*6

The unit of size: inch

What is a twin XL mattress?

Twin XL Size Mattress is the size above. The size of the box spring or bed frame to be purchased will be selected according to the size of the existing mattress.