This is a heater core for X1/9 cars without air conditioning.
50mm thick (measured at end tanks). Slightly thinner than that supplied in Fiat 124-series cars, but works just fine as a replacement. Applies to all model years.
Stock photo used for this item.
Good used condition. It has been reconditioned with internal cleaning, and pressure tested to 20lbs with no signs of leakage and unbent studs.