S

Pit to pit: 20.5".

Length of back: 25".

M

Pit to pit: 21.5".

Length of back: 25.5".

L

Pit to pit: 23".

Length of back: 27".

XL

Pit to pit: 24.5".

Length of back: 28".

XXL

Pit to pit: 25.5".

Length of back: 30".