Convert from braccio [Italy] to X unit

Unit Definition (braccio [Italy])
The Braccio is a traditional Italian measurement of length. The word means "arm", and a Braccio is approximately equal to the length of a man's arm, about 27 or 28 inches (68-71 centimeters). In modern times, the Braccio has become an informal metric unit of exactly 70 centimeters (about 27.56 inches), which is the same as the Arm Length unit.

Unit Definition (X unit)
The X-unit (symbol xu) is a unit of length formerly used to measure the wavelength of X-rays and gamma rays. The X-unit is approximately 1.0021×10-13 metre. Defined by the Swedish physicist Karl Manne Georg Siegbahn (1886-1978) in 1925, the X-unit could not at that time be measured directly; the definition was instead made in terms of the spacing between planes of the calcite crystals used in the measuring apparatus.