A tank body 125 comprising header tanks 120 of a radiator is composed with a polyamide composition containing polyamide 6,10, glass fiber, copper and nucleating agent. At this time, the polyamide composition contains, based on the total weight of the polyamide 6,10, the glass fiber, the copper and the nucleating agent, (a) 48.9 to 79.988 percent by weight of the polyamide 6,10, (b) 20 to 50 percent by weight of the glass fiber, (c) 0.002 to 0.1 percent by weight of the copper, and (d) 0.01 to 1.5 percent by weight of the nucleating agent, and the result of measuring half-crystallization time of the polyamide composition is 5 minutes or less. In addition, the polyamide 6,10 used has a relative viscosity, as measured in 98 percent sulfuric acid, of 2.3 to 2.9.