[Our size XS] chest: 30cm / 11.81 ", back: 20cm / 7.87" (approx.) [Our size S] chest: 35cm / 13.78 ", back: 25cm / 9.84" (approx.) [Our size M] chest: 40cm / 15.75 ", back: 30cm / 11.81" (approx.) [Our size L] chest: 45cm / 17.72 ", back: 35cm / 13.78" (approx.) [Our size XL] chest: 50cm / 19.69 ", back: 40cm / 15.75" (approx.) [Our size 2XL] chest: 55cm / 21.65 ", back: 45cm / 17.72" (approx.)